If your’re ASP.NET MVC developer you should already know about MVC Mini Profiler released by Stack Overflow, if you don’t, go get it now.
Google App Engine developers have the appstats, a tool that does similar things but requires you to explicitly look for profiling info.
Now GAE has mini-profiler to — this is old news apparently 😉 — an appstats wrapper mini app that you can embed in your web app, check out Google App Engine Mini Profiler and have stats in your face, all the time.