As described earlier, I'm working on a project dealing with RSS feeds.
Basically, I have a page which display RSS feeds. It grabs the feeds from a cache. The cache is updated by a script which periodically checks to see if all of the feeds are fresh.
The hard part is checking if the feed is fresh without actually downloading the feed.
There are some syndication rules that can be specified in an RSS feed -- but they're, to me, confusing. The easiest way, i found, was to use some standard HTTP tricks. Checking the "Last-Modified" header by sending a "If-Modified-Since" header or checking the "Etag" by sending an "If-None-Match" header seems to eliminate a lot of fuss. If only people used those headers more.