The definitive stamp family of France is larger by six members out of 100-stamp sheet since Saturday 1st March 2008 and the last rate rising. They certainly will be scrutinized in every details, like all definitives before. On the web, many ressources are now available to begin the climbing of this French philatelic mountain.
The Société des collectionneurs de coins datés et de millésimes (SO.CO.CO.DA.MI., litterally the Collectors of Corner Blocks and Millesimes' Society), created in March 1936, is known of every French philatelic magazines readers because it published the postage stamp printing dates and numbers. Its members compilates what they read on sheet margins, thank to gentle postmen who let them consult the stock or by investing money in buying corner blocks. The final goal is to study how postage stamps are produced and how this production evolves.
The Cercle des amis de Marianne (the Marianne's Friends Circle) publishes a little monthly study on their website, showing an aspect of one of France's 20th century definitive series.
The weblink pages of these two websites will help you climb another step of the mountain.
On the British side, the March 2008 issue of Gibbons Stamp Monthly saw the 11th and final chapter of Ashley Lawrence's study of the Sowers (la Semeuse). The Royal Philatelic Society London website proposes Lawrence's 2003 exhibition on these stamps too.