This site is almost like a quick one-page reference tool for teachers who are looking to refresh some of the basic W2L strategies...the admit/exit slips are mentioned, among others. I would use this site if I needed a quick refresher of a strategy I needed or wanted to implement for a particular lesson.
This is possibly one of the more relevent web sites I found for W2L strategies. Please scroll down on the homepage, and there is a list of links for informal writing ideas and strategies that help students develop a deeper understanding of what they're learning.