I like working with embedded systems and IP cameras are basically embedded systems with cameras, GPIO, and Ethernet attached. Perhaps best of all is how cheap they are on eBay.

Manufacturer	Model	Linux?	Notes
Gadspot	NC800	RTOS	Possibly SQ610D SoC
Gadspot	NC1000-L10	Yes	Same as the NC1000-W10
Gadspot	NC1000-W10	Yes
Gadspot	NC1200	Yes	Possibly the same as the NC1000
Vivotek	PT3112	No
Vivotek	PT3117	No	PT3112 + 802.11
Vivotek	PZ6112	No
Vivotek	PZ6114	No	PZ6112 + 802.11
Vivotek	PT7135	Yes
Vivotek	PT7137	Yes	PT7135 + 802.11