Scheepers Kitchen Garden Seeds Good herb & Asian greens selections; no photos
Seed Savers Exchange Great pics, lots of organics
Baker Creek Heirloom Heirloom, huge selections (8 pages of tomatoes), not much growing info, not all depicted
Johnny's Organized by category, good growing info
Stokes Commercial catalog has a ton of growing info and mostly hybrids
Seeds of Change I'm ticked because they increased packet prices 50 cents--nearly a 20% increase; NM farm that grows organics--PURCHASED by M&M Mars in 1997
Shumway's

The Chile Woman My friend Susan ships transplants of chiles, peppers, tomatoes & tomatillos, $3 per plant
Abbondazza in Boulder http://www.eatabbo.org/seeds.html

General sizing/planting info: UofI Extension
Garden forum: Dave's Garden (although use Google search, as they are paid forums)
Seed starting chart: http://www.almanac.com/garden/plantingtable/index.php