I saw a link to “Mail.appetizer”:http://www.bronsonbeta.com/mailappetizer/beta/ on LifeHacker, and decided to give it a shot. I have been using GrowlMail, but it tends to lock up Mail for a log time as it parse through the 50 new messages I get each morning.

Mail.appetizer doesn’t seem to have that problem, plus you can read most of the message and do some basic message management right from the popup, making it pretty useful.