Doctors' Lounge - Help! Pill ID a discussion board where you post the info you have, and the on-line doctors and pharmacists will try to help you. Much slower than link-driven sites, obviously, but your answer will be correct.
Drug Image Search from Drugs.com, a visual-based search engine for pill ID.
Drug Information Center from "A Healthy Me", a link collection covering all aspects of drug use; the ones on pill ID comprises a short but useful list.
FAQ: Pill Identification a short monograph on pill ID from the National Library of Medicine (part of NIH).
Pill ID Resources a collection of approaches and databases to help ID that pill you totally forgot about. Also features a line of timed medication dispenser systems; many of the dispensers can be locked.
Pill Identification Tool from WebMD, this is very easy to use and feaures a huge database, so you're likely to ID your unknown pills. Just enter any letters or numbers on the tab, its shape and color, and in a second you'll have the answer.
Pill Identification Wizard from Drugs.com very easy to use. Enter what physical features the pill has, and the program returns a selection of images of pills that match your description.
RxList Pill Identifier just enter any imprint on the pill, its color and shape, and you learn what your pill is
Tools and Resources for Pill Identification a small collection of links from MIT.
What's My Pill? from Pharmer.com, features a short discussion of each drug class, with hyperlinks to images of every pill mentioned. Much more useful than it sounds!