Nikhil has a very cool IE Helper/HttpModule combination for download on his blog, which does

• Warn you when debugging or tracing is enabled
• Extracts trace information from a page and shows it in a separate window
• Shows decoded ViewState/ControlState

and all from within IE…very cool!

UPDATE
new version can be downloaded here. The ASP.NET cache can now be viewed and purged + you can recycle the application for testing purposes.