If you're after some really cool Geographical Information System (GIS) software, check out Manifold.net. They're up to version 6 now (I started with v2 I think, back in the mid-90s). This product rocks. It has all of the functionality of it's far more expensive competitors, at a small fraction of the price. Check out the Internet Map Server (still currently a classic ASP application by the look of it).
One of the coolest things is that the Manifold team have converted their entire code base (1M + lines) to managed code! They're ready for the 64-bit versions of the OS and the .NET Framework. This thing already flies, I can't wait to see the 64-bit version.
There's also a great discussion about why they've steered clear of the *nix platform when practically all of their competitors have ports for multiple platforms.
Finally, the Manifold community is the second-most active and helpful online community I've come across, and the tech support and transparency from the Manifold staff is simply sensational.