I'm not sure how official these logos are.  But, like Google logos, I'm going to collect.

2nd Birthday of Gmail - April 1, 2006

Valentines - February 14, 2006

I don't have the full logo from this day, odds are it was like 2005, which is below, but apparently GMail again recognized the day.

Happy Thanksgiving - November 24, 2005

7 things the Gmail Team is thankful for this year Our families... 4 engagements, 7 weddings, 11 new babies, 1 reunion, and 1 cross-country move by a fiancée so they "don't have to do the long-distance thing anymore" so far this year. Each other—the little family we've created here makes it fun to come in to work, especially on days when we play kickball. Winning the "PC World World Class Award" for being #2 on the list of The 100 Best Products of 2005. (We don't mind being #2, especially to Firefox. Plus, it gives us more to work for.) Google Video, and one fan's video we love in particular. The horn of plenty and the guy who drew it. You, our users. Yes you. Again. Still. Cheese. Brie, goat, cheddar, the stuff we write on our home page... :) Happy Thanksgiving from the Gmail Team!

1st Birthday of Gmail - April 1, 2005

Valentine's Day - February 14, 2005

New Year's Day - January 1, 2005

Thanksgiving - November 25, 2004

This version is used in Germany only, due to Daniel Giersch possessing the rights to "G-Mail" in Germany. It is also now being used in the U.K.

I don't know if this is official or not, but it looks like it could be...

The original Gmail logo before talk: