Here are some of the main features of the T-Mobile SDA. Please add more fun features that you've used on the SDA

Size	4.53” (H) x 1.82” (W) x .69” (T)
Weight	106 g (with battery)
Memory	ROM: 64MB; RAM: 64 MB DDR; MiniSD Expansion slot
Keyboard	12 button numerical dialing keypad, along with text entry
Display	Large 2.2” (QVGA) bright, 64k color TFT LCD
Navigation	Thumb-operated 5-way navigation pad and soft keys
Phone	Integrated earpiece/microphone, along with integrated speakerphone
Network	850/900/1800/1900Mhz GSM/GPRS/ EDGE Networks
User Interface	Microsoft Windows Mobile 5.0 for Smartphone
Notification	LED, MP3, Polyphonic, Vibrate, on-screen message
Ring Tones	MP3, MIDI, MPEG4, H.263, WAV, WMV by WMP
Bluetooth™	v1.2 compliant; Hands-free headset and car kit profiles supported
Wi-Fi	IEEE 802.11b
IrDA	Infrared enables short-range wireless communication
Camera	1.3 Mega Pixels; Night Mode and Preview Mirror
MP3 Player	Listen to your favorite music on-the-go