Here's a list of the site's I see commonly mentioned in such posts. It includes the O.R.G.& H.P.S. link.

The Seed Site - http://theseedsite.co.uk/index.html

Backyard Gardener Seed Germination Database - http://www.backyardgardener.com/tm.html

Ontario Rock Garden & Hardy Plant Society Seed Germination Guide - http://www.onrockgarden.com/guide/seedguide.htm

Tom Clothier's Germination Database - http://tomclothier.hort.net/

B&T World Seeds Database - http://b-and-t-world-seeds.com/