First of all, there are many sites where you can find the full text of the EU Constitution and many detailed explanations, so if you want to have lots of information, you can go there:

Official site of the European Union on the Constitution, including the full text of the Treaty (pdf, 860 kb), links to the various institutions of the European Union, and some interesting Powerpoint presentations (pps, ca. 400kb);

The site of the UK Foreign Office on the topic, including their commentary of the treaty (scroll to bottom of that page);

The European Convention, the group that negotiated over two years the Treaty which was finally adopted by the Heads of Governments one year later, with small amendments;

The BBC Special on the topic, including a summary of its main terms and explanations on the various institutions and decision making mechanisms.

Two of these sites are European, and two British. There is an untractable problem when discussing Europe in English - the perception bias. As you hopefully know, the UK is the most Eurosceptic country in Europe, and this means that, as a general rule, commentary in English about Europe is more critical, distrustful and dismissive of Europe than the general European public is. Being French and strongly pro-European, I will of course strive to fight that perception bias with a bias of my own!

So here we go.

I will not go into a detailed history of the construction of Europe (you can find a British-slanted timeline here courtesy of the BBC), but the idea of the Constitution came about after the disastrous Treaty of Nice, in France in 1999, which then set the parameters for decision making once the enlargement to Central Europe would take place, and which is unanimously considered to be a terrible treaty, with complicated and impossible to explain rules, and very unwieldy voting procedures. The brain child of Chirac and Schroeder when they did not get along, it has come into force last year and will remain in force if the EU Constitution is not ratified.

Faced with that perspective, the European countries decided that it would make sense to try to simplify the rules of the EU, make them clearer to everybody, and hopefully improve the decision-making processes in an union of 25. Thus the European Convention, was born, regrouping representatives of the European Commission (the European executive body), the European Parliament, each national government and each national Parliament, 115 members in all, led by Valery Giscard d'Estaing, the former French President in the 1970s. They worked for 2 years to find a consensus, and it was almost mission impossible as there were so many conflicting requirements and wishes (more federalism, more subsidiarity, more powers to the Commission, more power to the member States, more social norms, etc...) and it is a significant achievement that they managed to produce something in the end.
This is important to note: this document is the result of negotiations between representatives of all countries (including the Central European countries which were not members at the time), where both euro-federalists and euro-skeptics were represented, nationalists and federalists, left and right; it was done in an open and transparent debate which was discussed in each country, and the result was a real pan-European consensus (and Giscard d'Estaing deserves a lot of credit for driving this massive debate to a successful conclusion)

The document was tweaked by the heads of States a little bit, but was kept essentially as prepared by the Convention; it was agreed  on 18 June 2004 by the Heads of State and signed on 29 November 2004. (A first attempt to agree on the document failed in December 2003 because of a disagreement between Spain and Poland on one side, and most others, lead by Germany and France, on the other, about country weighting rules for majority votes. The change of leadership in Spain in March 2004 helped unblock this situation)

Its content can be summarised as follows:

• it consolidates all past European Treaties into one single, better written document
  
• it gives a legal personality to Europe
  
• it creates a President of the European Council and a Union Minister for Foreign Affairs
  
• it extends majority decision making (as opposed to unanimous) in the Council of Ministers to a number of new fields, including justice and home affairs, and provides for more co-decision powers to the European Parliament
  
• it puts in place new voting procedures (a system of double majority voting from November 2009: decisions will need support of 55% of countries, representing 65% of EU population)
  
• for the first time, it makes it explicit that Member States can leave the EU if they wish
  
• it incorporates the Charter of Fundamental Rights

It is a tidying exercise, with, as usual, a few more powers given to the European institutions here and there. The main changes are symbolic, through the creation of more visible representatives (the Union chief diplomat, and a more permanent President), through the name of "constitution" itself, and through the Charter of Fundamental Rights. It adds prerogatives to the European Institutions in what are eminently sensitive political issues, and while the substance is not all that different, it is widely seen as a new step towards the creation of a political Union, complete with executive (the Commission); legislative (the Council of Ministers and the European Parliament) and judicial (the European Court of Justice) powers.

As an aside here, Europe has always been a political project, and has always been seen as such in France and other "core" countries. It has been sold to the British public (and thus to the English-speaking world) as an economic endeavor, and that misunderstanding has been the source of many problems, as the British public smells the politics, is more reluctant to go there due to its specific history in Europe, but has Europe rammed down its throat for "economics" reasons which, of course, do not tell the full tale. In France, it is more the other way round: the population likes the political project part, but not so much  the economics ("a vast laissez-faire anglo-saxon conspiracy")...

Now that the Constitutional Treaty has been agreed and signed, it must still be ratified by ALL Member States to come into force. Ratification can be done by a vote of Parliament (as Lithuania, Slovenia and Hungary have already done) or by a referendum (as done recently in Spain, and as will be done in France, UK, Netherlands, Denmark, Luxemburg, Ireland, Portugal, Poland and the Czech Republic - see the map in previous link).

So this gets us to the French referendum, which is due to take place on 29 May 2005.
Polls showed initially a strong margin in favor of the "Yes", but this margin has shrunk, and two recent polls have shown for the first time a small majority for the "No". The mainstream parties of both left and right are campaigning for the "Yes", but there are opponents on both sides, nationalists on the right (or "sovereignists"), and the hard left (Communist party and other assorted extreme left groups, as well as a significant minority within the socialist Party). A lot on issues unrelated to Europe are influencing this vote, and I will go into these in coming installments. The main topics of discussion are the following:

• the adhesion of Turkey, while formally totally unrelated, is very present in the debate;

• the Bolkenstein directive, liberalising services within the Union, has become a bogeyman in recent weeks (mainly because of the concept that service providers could do business in one country while respecting the laws of another Union country);

• the general unhappiness over unemployment, lack of revenue growth, and a general sense of social malaise;

• a desire to punish Chirac who appears out of touch, and a desire on the left not to give him a boost with a referendum victory (after having being forced to vote for him in 2002 against Le Pen);

• a perception on the left that the Constitution is too business-oriented and not "social" enough;

• jockeying on the right in the perspective of the 2007 presidential elections (and possibly before that of a change in the Prime Minister, the current one, Raffarin possibly to be fired after the referendum)

• a general feeling that France has lost its dominant place in Europe and that Europe is no longer exactly a tool of French influence and grandeur.

I'll stop here for today. don't hesitate to ask questions, I'll try to respond in comments or in future diaries. I hope that other European posters can contribute with their experience of the debate in their country