Hey guys and gals, I'm a long time listener, first time caller. Just published an interesting project to http://www.plogress.com It consists of a seperate blog for each US senator and state representative, that right now just lists bills that he or she is sponsor of or cosponsor (I hope to add votes and committee activities later).
I use perl scripts (I know, php would have been more consistent, but I had the pieces already written) to gather the data and update each blog. Each blog has its own install, and they all share the same database, with common user and categories tables. Looking back, I probably could have had all of the blogs share most of the files, and just had an unique index.php and wp-config.php for each blog. With a little more work, I could have had them all share the same tables, but the current setup seems to work pretty well. The only pain in the butt part is if I have to change a file (like upgrading the wp-blog-header.php file), I have to make over 500 changes. I do this with via ftp and a perl script also.
Anyway, thought I'd share this with you guys, if you have any questions or comments, I would welcome them!