There's no need for Lighttpd when you use Nginx. It can do everything that Lighttpd can do and more (and has no memory leaks).
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.
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.