[Via Paul Andrew] Now here is a must have tool for every SharePoint developer that wants to make sure that his code isn’t causing any nasty memory leaks due to forgotten Dispose calls (typically on the SPSite and SPWeb instances)! The SPDisposeCheck utility can actually review a compiled assembly and tell you if there are any forgotten Dispose calls, so you can even check third party assemblies. But remember, it’s a tool: nothing beats a full code review, but it certainly speeds up the process.
Get the detail's on Paul’s blog: SPDisposeCheck is a tool to help SharePoint Developers follow memory management best practices when using the SharePoint API with IDisposable objects including SPSite and SPWeb. This tool is not supported by Microsoft and is recommended to be used on Developer workstations and not on production SharePoint Server installations.
Download from http://code.msdn.microsoft.com/SPDisposeCheck.