Pablo Galiano, one of my friends and colleagues from my patterns & practices days, has just released a very cool extension for Visual Studio 2008 called StickyNotes. As the name suggests, it allows you to attach sticky notes to your code, with a lot more richness and less intrusiveness than regular code comments. You can also choose between personal notes (visible only to the person who created it) and team notes (visible to the entire team).
Unfortunately my team is still using Visual Studio 2005 (we started before VS2008 was released and haven’t had time to upgrade yet!), so I haven’t been able to use this on my project yet, but I have played around with it and it looks very nice. And while this tool isn’t free, at $US9.99 (about what I pay for lunch) it’s practically free. Give it a try!