RSS feeds are handy not just for people who use feed readers such as Google Reader to keep up with their favourite sites, but also for bloggers who may wish to feature recent posts from other sites in a single widget. ChimpFeedr is a very basic webapp that can mashup RSS feeds for both uses.
It's easy to create a mashup feed. Enter the address of each feed you want to add and then click 'Chomp Chomp'. After a few seconds you'll be given a link to your mashup feed which you can then enter in your preferred feed reader or feature on your page with a widget.
If you'd like to mash a few feeds like a chimp mashes bananas, check out the link below.