Of course, Affiliate-Schemes.Info is your primary resource for all things affiliate, but believe it not, there are some other sites out there too which are worth reading.

UK Affiliate Marketing Forum
http://www.a4uforum.co.uk/
Interesting forums on all the affiliate networks plus other related subjects such as web promotion.

Affiliate Seek
http://www.affiliateseek.co.uk
Affiliate program guide and news with searchable listings.