Slow Scan TV (SSTV)
SSTV is a fun mode, can be done on any band with the right equipment, and is easy to operate. You can transmit via HF, VHF/UHF Simplex, or even through a repeater (though you have to be mindful of the timeout on the repeater). You'll need a Rig, Computer (w/Sound Card), and a Sound Card Interface. 14.230mhz on 20M appears to be the most active band currently.
Below are some links to information, hardware and software to get you started :
SSTV Info
Getting Started with Slow Scan TV http://www.arrl.org/tis/info/pdf/99753.pdf
An SSTV Primer http://www.valbrembanaweb.it/gor/iz2dpz/SSTV/
Understanding Sound Card Interfaces http://www.qsl.net/wm2u/interface.htm
More SSTV Info http://www.sstvham.com/
Sound Card Interfaces
Rascal http://www.packetradio.com/
Rigblaster http://www.westmountainradio.com/
Signal Link http://www.tigertronics.com/
SSTV Software
MMSSTV http://users.chartertn.net/kf4hou/mmsstv.htm
SSTVPAL Multi Mode http://www.kiva.net/~djones/