Yahoo! Mail Search
Dunno if this is a new feature, i noticed it just now. I’m currently using the AJAX version of mail ( which is out of beta unlike a certain competitor). Searched for a particular keyword and got the results in a new tab. Nothing new about that. But thats when i noticed that the sidebar on the right (where the ads are usually displayed) had a “Narrow Results” column with some options. It actually sorts the results on various parameters like sender, folder, date, type of attachment and message status (with the number of search results for each). Of course you could do most of this in Gmail as well, using the advanced search feature and typing all the parameters manually. Yahoo! Mail does it automatically. Pretty neat.