Yahoo Pipes allows anyone to create their own mashup in a method very similar to creating a flowchart.
After messing around just a little I was able to create 2 pretty cool little mashups:
The first one geocodes garage sale locations and puts them on a map. Not very well, but it was really easy to do, so it was still worth the effort
The second one combines 5 different Job search feeds into one, checks to see if the titles are unique, and then sorts the results in descending order by published date. I still prefer indeed.com for looking for Job information, but if I can also grab the feed to format myself to fix those problems.
All in all, it’s pretty cool stuff. I think I have a real world use for an aggregated real estate news feed on www.webdigs.com already