Raymond has a great post on the history of PowerToys. I'm proud to be a member of this family. The first code that I ever wrote using VB.NET shipped as the Dictionary Tool for Tablet PC, and my latest PowerToy, Send to OneNote from Outlook was a result of hundreds of man hours of leaning how to write (and deploy) managed code for Outlook. I think the first project (learning to program from scratch) was actually easier than the second :-).
One might wonder how you turn two projects like this into PowerToys. Well I am not a member of the Tablet PC team, nor am I a member of the OneNote team. I wrote both of these when I was in the MacBU. I'm a member of a lot of dogfood/product distribution lists at Microsoft (social hangouts for geeks). It's one of the cool things about Microsoft... we have these private internal product love fests over email, and most of the time we get to try new builds, ideas, etc. Well I happen to be on a Tablet DL and a OneNote DL and when I finished my two projects, I sent out some emails letting people know they could try them. In both cases folks on the respective teams proposed shipping them as PowerToys. Getting them out the door isn't as bad as Raymond says, but it's not easy. You basically need some level of basic testing, and the dlls and exe's must be code signed using your smartcard, then signed by Microsoft. It's really a matter of time and resources.
I actually think that it would be great if Microsoft had an incentive program, or allowed employees to work on collaborative PowerToys and ship them. There is so much cool software internally.