I've been spending some building a little project lately (not directly CRM related). My goal was to try out a bunch of technologies instead of going for the classic web page + database architectural pattern. Some of the technologies explored were:

• Amazon's SimpleDB. Hash table in the sky. Good docs and samples made this a breeze.
• Amazon's S3. It will be interesting to see the optimal pattern (and price) between storage in SimpleDB vs S3.
• Amazon Simple Queue Service. You don't hear a lot about this (which is surprising). If you need to broker connections between disparate infrastructures then this service is for you.
• Ruby on Rails. Urgh. I started with an open mind and almost wanted to become convert. I generally like the 37-signals stuff (although lately it's been loosing some of it's shine in my eyes). After hitting limitation after limitation I gave up. Now I'm downright frightened by 37 Signals given their paternal relationship and reliance on RoR. This technology was the biggest disappointment.
• ASP.NET with Framework 3.5. This was the easiest in IMHO. The only thing lacking is an RTM of Visual Studio 2008 Web Deployment Projects.
• Generics in Framework 3.5. Generics are one of those things you think you fully understand until you need to use them. It's a nice implementation but it feels like this will need C# 3.0 to really 'shine'.
• LINQ over objects, XML and SQL. I was surprised at the quality of the documentation here. LINQ is actually pretty easy to learn but we (Microsoft) don't make it easy. MSDN was filled with out of date documentation and poorly explained samples. However I'm a convert and I can see myself using this in most future projects. LINQ over my customer objects was particularly powerful especially when combined with backend storage on SimpleDB and S3.
• Carnegie Mellon's ReCAPTCHA. This is a great component which lets your users help with book digitization while proving they are human.
• Windows Live ID Web Authentication. My app doesn't really need a user database but I wanted some rudimentary auth to help slow down spammers. Having danced with Passport before I was fearing a long night with a cup of espresso and some nasty looking COM objects. This wasn't the case! The dev.live.com people have done a great job of opening up WLID to the masses. I had my auth up and running in minutes. I was tempted to add Windows Live Alerts - but you need to email them to set up your account (ie. too much trouble).
• Free Text Box. I'd seen this project around and wanted to give it a go. It's free for personal use (so I won't be distributing my little project - unless I cough up $200). I found a few rough edges but you can't complain when something is free.