I've blogged quite a bit about how happy I've been with the Yahoo APIs (although I can say that they don't seem to respond to bugs well - I found a bug that was reported, and acknowledged, by Yahoo a year ago that still hasn't been fixed), especially in comparison to Google. Today I discovered Yahoo Pipes. Yahoo Pipes is a graphical tool that lets you build complex mashups between various RSS services. The tool is absolutely amazing and you have to give it a try.
In about five minutes I built a pipe that joined the RSS feed of MXNA and Joystiq and sorted them by date. You can view the RSS feed here:
The tool allows for some pretty complex mashups. You can filter, accept user input, sort, etc. Check it out.