You can browse the Mercurial repository online at this URL: <https://bitbucket.org/pygame/pygame/src>.
You can also make a checkout with this Mercurial command:
hg clone https://bitbucket.org/pygame/pygame
You can find development binaries at The Spectacularly Adequate Automated Pygame Build Page. After every hg checkin, Mac and Windows binaries are built, tested, and then uploaded.1
Compilation instructions can be found in the Pygame.org wiki: <http://pygame.org/wiki/Compilation>.
1 — Not yet moved to Bitbucket.