Jeff Fedor posted a short list of some early stage companies in Waterloo that are expanding and hiring—Miovision, Primal Fusion, AideRSS, and Covarity (you can add Tungle to the list, which is looking for someone with Java expertise). Other than Tungle, all of those companies are using the Waterloo Tech Jobs website, which seems to have improved a bit since the last time I looked at it (it's a Communitech initiative, and I work with Communitech, but it's not something I'm involved with at all).

Any local startups are certainly welcome to use the WatStart site as well—you can put company information on the wiki (under the local startups page) and make posts in the forum.