I spent way too much time today hunting down this tip. I’m writing it here for my ease of recall.
Often times, developers in WSS3.0/MOSS2007 probably run across the issue where a web part is dropped on to a page and then Sharepoint errors out for one reason or the other. Sometimes, the user is directed to a Web Part Maintenance page, which helps the developer remove the offending web part from the page. However, there is no way to get to this page from any easily available link. If you are seeing the ASP.Net "Yellow Screen of Death" then you need to disable the offending web part.
In order to get to the Web Part Maintenance page for ANY sharepoint url, try the following trick.
Append the querystring ?contents=1 to the url in the browser as shown below