CU CS PhD Requirements page
Every student's one-stop summary page to track progress within the program. It _is_ a high-level page though, leaving a lot of necessary details out; details that currently has to be tracked and collated from disparate sources.

Citeseer
Despite a kludgy interface, Citeseer manages to provide some unique ways of searching for and limiting the range of papers returned: e.g. by date, or citations. There seem to be quite a lot of documents (old and new) that were not actually in it's database, resulting in a trip to Google Scholar to find them. Confirming my findings is this Wikipedia entry: "CiteSeer has not been comprehensively updated since roughly 2000. It should not be used as a representative sampling of current research."

ACM
Although the ACM collection is limited to papers published by ACM, the portal provides a very necessary and more helpful citation system that beats the pants off the other two. Being able to see a history of collaborative colleagues is another good way to feel out the breadth of an authors research interests. The citations are both in Bibtex and Endnote formats; a time-saving feature. This resource isn't free, however, as you have to be a member or on a member campus to download articles.

Google Scholar
For when you can't find the actual paper (not just annotations about it), Google Scholar comes to the rescue. It allows one to find papers usually on the authors site (if they've made it available), without much restrictions restrictions. This engine also has a nifty "Find it at CU" (or some other institution) feature.