As things currently stand the only option is AROS. MorphOS powerbook support has been mentioned for a while, but as of yet isnt supported. As for which aros laptop to get, despite what some people might suggest Id steer clear of an Asus Aspire, for no reason other than theyre kinda crappy. They are well supported, but ATOM cpus are particularly weak, especially when you remove hyperthreading from the equation (which aros doesnt support). There must be a bunch of old 1-1.5ghz-ish pentium3, or athlon based laptops out there what are supported too, and they'll be much faster than an atom.
A rough guide for supported hardware goes a little something like:
gf1 through gf9 based cards (gts 250 is a renamed gf9, so also supported). This is probably the best option for gfx being its the only option with 3d acceleration (even small amounts of 2d acceleration is done via gpu for gf cards). ATI cards from things like rage pro through to radeon x850, and also newer (some radeon hd cards, but I cant be more specific here). Intel gma is also supported. Both ati and intel are 2d accelerated only though.
For sound you have intel hd audio (also includes some realtek codecs if Im not mistaken) ac97, sblive/audigy, sb128, and a bunch of others (going by memory, so please excuse the vagueness).
For wifi I think the only options ar some atheros based chips plus old prisms2 devices.
Feel free to ask for more details and I'l try to provide them.