Yahoo Pipes allows you to manipulate rss feeds. I built my first very simple pipe this morning. It takes the Amazon Gold Box feed and strips out the Baby Deals. You can also much fancier stuff like match geocoded addresses in feed items and modify the content of individual items. Too bad they don't provide a way to screen-scrape pages to build feeds.
If I build any more pipes, you'll be able to find them on my pipes page.
I've written my first greasemonkey script, to rewrite links to JSTOR. JSTOR contains articles from tons of journals, but you need to have a subscription to access it. My university has a license, but in order to use the site remotely, you must go through the school's proxy server. So my script appends the name of your proxy server onto the jstor.org domain, in my case libaccess.sjlibrary.org.
Update: It now supports ieeexplore.ieee.org url's too. I knew the name would come back to bite me. I guess I'll wait to rename it until I rewrite to handle multiple domains more cleanly.
Another Update: Support for
The state is that great fiction by which everyone tries to live at the expense of everyone else. - Frederic Bastiat