We just had a look at the laptop shops during the felicity, after some discussion with the vendors we arrived at the conclusion that HCL laptops would be the best buy for any one. First those guys provide good configuration, Second they have good service, Third they don't trouble you with OS installation and stuff.
The third point is worth consideration, HCL vendors not only give you freedom to put OS of your own choice during the purchase but also change it later without bothering to inform them. All others vendors have at max single installation system that too is fixed when you buy the laptop. Toshiba will provide option to install Linux in the beginning but their models are very restrictive.
Acer too provide Linux installed machine, but I think they will also not be flexible with the dual OS installation if some one needs. Cost of a HCL laptop will probably the best offering for that configuration, which is what made them so successful at Desktop purchase in IIIT too.
Also note to ask hardware compliance with Linux when purchasing a laptop. The simplest option is to put a Live CD in the laptop's CD/DVD Rom and check if all the hardware is supported.