Some things I've always found helpful are the control galleries on the ASP.NET and Windows Forms web sites, which is a collection of free community-submitted custom server controls, free for public download.  This is a great locale I've tapped many times, either for production-quality utilities, just to see what people are working on, or to get inspiration for my own projects.

I thought a lot over the weekend about the effort into the Atlas Project being put forth by Microsoft, being built largely on the growing demand for AJAX-style programming.  User libraries like Sarissa are starting to popup more and more, and there are even some specific to .NET, like that developed by Michael Schwartz.  Both are very cool.  I'd like to see such community libraries by aggregated into a central locale by Microsoft, true to form with the existing Control Gallery concept, giving us a place with high-visibility for such libraries to be stored and accessed.

I would think this would make incorporating/integrating the libraries into Atlas a little easier and give the platform some nice momentum as it reaches completion (if indeed by the time Atlas is ready for RTM it'll be as easy as referencing such a library in your page's code...I'm not going to make any assumptions).

What do you think?  If anything, it's directly more under Microsoft's control than, say, Sourceforge.  :)