This document discusses how Caltech, a science and engineering university located in Pasadena, CA, can use online communities to connect with its 21,000 alumni. It notes that Caltech has around 2,100 students, with 900 undergraduates and 1,200 graduates. The Caltech Alumni Association, which has around 9,000 members including students and postdocs, is looking to online communities as a way to engage its large number of alumni. Examples of online communities that could be used are provided, such as Facebook, LinkedIn, and virtual worlds like Second Life.