[iamgabeaudick]

Reverse Craigslist - Allow a user to enter an anonymous Craigslist email address (that they had previously replied to) and their city, and then return the post that contained the email.

The reason being: When looking for something on Craigslist, I often send similar emails to several potential sellers. But then, when they reply, I have no way of knowing which posting was theirs (and the link to it). (Of course, you could contain the link to the posting you're referring to in each email, but that's a hassle that I'm sure most forget to do.)

[vbhavsar]

You can just enter the url of the Craigslist post at the end of your mail.

[blehn]

If you click the mailto link in the listing (not copy and paste it), your email will be pre-populated with title of the listing as your subject line, and the URL in the body.