I've used Google Reader for some time to read RSS feeds and while it is perfectly adequate for this task, I wanted something that would send me the data via email as soon as it was posted, rather than having to open up Google Reader periodically to see new posts or monitor the feed in my Mac OS X Mail client.
After looking all over I couldn't find any option for this in Google Reader and finally ended up with a web site called FeedMyInbox.com. It does the very simple task of monitoring the RSS feeds I give it and emailing me when a new post appears. You can have it send you each new post as it appears, or a daily summary. FeedMyInbox lets you monitor up to 5 RSS feeds for free, after that they start charging for the service at varying rates. I find this service especially useful for monitoring items for sale on craigslist. It lets me quickly respond to new posts.
I’m actually picking up a small utility trailer today that I found via FeedMyInbox and Craigslist.