What's the best way to manage a slew of browser UI tests? I'm looking for an approach that may have worked for you in the past when dealing with numerous automated browser tests. Obvious answers such as "they should be refactored into lower-level UI tests" aren't what I'm looking for. Ultimately these tests are incredibly time consuming to both run and maintain. I'm looking for the best ways to minimize this problem.
I must also mention that I'm confined to free software that's particularly focused on .NET (WatiN, CC.net, Fitnesse, etc.).