Affiliate software recommendations?

[Speedie]

Hi,
Can someone recommend some php/MySQL based affiliate software? I'm looking for something straightforward that allows you to pay a commission to affiliates based on individual sales, preferably with a large userbase and an active help forum.

[webit]

idevdirect

[MinuWeb]

postaffiliate
(basic version is free)

http://www.qualityunit.com/postaffiliate/