Upgrading to OS X 10.7 (Lion) has really caused some issues for me. A big issue for me was not being able to easily grab the current clone of ffmpeg from the git repository. I was able to compile after doing the following.
1. Get your OS X 10.7 system current (as of now 10.7.1 is the latest and greatest)
2. Get Xcode from the App Store and there will be a software update on that (unless Apple has recently changed that.)
3. Reinstall fink (recommended after the 10.6-10.7 upgrade) and get it fully up-to-speed. http://www.finkproject.org
4. Install pkgconfig via fink using
# fink install pkgconfig
as root or do it with sudo.
5. Get (git!) the current clone of ffmpeg. (info here —> http://ffmpeg.org/download.html )
6. When you do the ffmpeg source configure, include the –disable-yasm flag
# make install
7. You will have ffmpeg on OS X Lion.
Hope this helps.