For the past two years or so, I've constantly worked with customers on issues related to not properly disposing of SPSite/SPWeb and other objects when necassary in long running applications, web parts etc. We've pushed for SDK updates etc where necassary, but we didn't have a complete "Developers Guide" on this subject alone.
Scott Harris took the initiative and took all the hard work that I, Chris Gideon, himself and others have struggled with over the past two years and put it into a great document along with Mike Ammerlaan (A PM for the SharePoint Product Group)
After many weeks of composing, reviewing, editing, fact checking 🙂 We've completed it and it is now available:
Best Practices: Using Disposable Windows SharePoint Services Objects
Hope this helps, as it's part of my daily mantra with folks when I discuss this. (Now I need to go an make sure I'm practicing what I preach in my tools :))