I\'m just learning how to do things, and want to start using some sort of version control for a web app.
What\'s most appropriate for deploying a python or php web a
Subversion is a good choice. For the client, there's TortoiseSVN (http://tortoisesvn.tigris.org/) that integrates with the shell and lets you do things with a right click on a folder. For integration with Visual Studio (I'll assume that's your environment) there's VisualSVN (http://www.visualsvn.com/) and AnhkSVN (http://ankhsvn.open.collab.net/). For the server there's a one-click installer you can find here (http://svn1clicksetup.tigris.org/) that does the setup in a snap. VisualSVN also has a (free) server that you can use which provides it's own web access and security (rather than using apache) and has a mmc-snapin for managing/creating repositories and users.
I once used Perforce and was impressed with it. There's GUI and command line versions and it supports Windows, Linux, Mac and Unix for both the server and client. It integrates with Eclipse and has APIs for writing your own client applications (C/C++, Ruby, Perl, Python) It only supports two users and five workspaces before you need to buy licenses though (but that is within the scope of this question).
Personally I use monotone, learning a DVCS is definitely the way forward.
SVN would been my first choice. If I have to take a second choice I would go to CVS.
While I like svn a lot, I've found mercurial handy for having the whole repository locally. (the same goes for git, but its interface is a little less polished in my opinion.)
I'm using unfuddle.com and I love it. It's free for a one person web app