Stephan Deutsch ran into this review of an external graphics card adapter that can blow new life into your old laptop. The procedure looks simple enough and the results are impressive!
I stumbled across this DYI review of a 50 USD device that allows people to use an external graphics card from a PC on a notebook.
It might be interesting for those blender users who happen to possess an nVidia graphics card (or can lay their hands on one cheaply) but do all their stuff with (older) notebooks and thus have issues using Cycles and GPU rendering. The review uses it solely for gaming, but I think as soon as the card is recognised in the OS, it can be used in Blender as a GPU render engine.