Daylilies in general

The American Hemerocallis Society
The Daylily Place
Tinker's Daylily Discussion Forum

Phenology
Phenology Web Links
The Lilac Phenology Network Home Page

Pests
Bulb Mites (Please note this article mentions using Kelthane to control bulb mites. It has been suggested elsewhere that this product may not be safe to use on daylilies).
Bulb Mites in Ornamentals
Pests Section of AHS Daylily Dictionary
Lesser Bulb Fly

Leaf Streak Fungus (Aureobasidium microstictum)
Plant Pathology Circular on Leaf Streak of Daylilies (PDF)
Acrobat Reader (needed for the above link)