RegNamespace sample up on codeplex
Scott, Jerry, Thayn and I have whipped up a sample of indexing the registry, as well as a shell folder (namespace extension) for viewing it. It's great to be able to search the registry via the index and it's great sample of how to create a shellfolder, protocol handler, and even an IFilter. So head on over to the codeplex site and check out the source code, or if you're more interested in having it than seeing how it's build, just download the binaries and enjoy!
This is something that we're looking to improve over time, adding features and generally fleshing it out to be a rich, complete experience. We're not yet to feature parity with Regedit, but it won't be too long.
If you're interested in samples related to shell programming also check out shellrevealed.