T-Mobile offers the thin slider phone Samsung Blast (aka SGH-T729).

The T-Mobile exclusive Samsung Blast features an eye catching red and black case design. The Blast is the first T-Mobile phone to provide direct access to personal e-mail, including AOL email, Yahoo! Mail and Gmail, making it easy to check messages anytime of the day. For added convenience, e-mail messages on the Blast can be read and responded to for the same pricing as text and picture messages - no data package necessary.
Other features of the SGH-T729 include a 1.3MP camera, 262k TFT color display with 176x220px resolution, QWERTY-like keypad with T9 predictive text, MP3 player supports MP3 and AAC, GPRS/EDGE and Stereo Bluetooth.
Via T-Mobile. Buy the T-Mobile Blast on Amazon.com.