FastCGI for no particular reason other than it's worked for me straight off using a couple different Python versions and Django.
I also use nginx as proxy in front of apache and dev instances of django manage.py runserver (nginx serves up static, passes dynamic on to back ends)
Nginx is so powerful, flexible, and has never given me a single problem. I loves it.
Wow. This was brain freaking dead simple to configure compared to Apache and even simpler than Lighttpd. Thank you a million times over! It works great!
Our app is Python 2.5 and Django (well, kinda Django). I haven't gotten to deep into the Lighttpd thing yet, but it looked promising. Maybe I should take another look at Nginx?
Also, do you recommend FastCGI or WSGI? I've had a hard time figuring out precisely what the differences in implications are.