I had very limited funds when my last laptop broke, so I was looking at low-end laptops with linux last December. I bought a HP 625 laptop for €400 that came with linux out of the box (you could also get it with windows, but that had less RAM and a smaller harddisk for the same price b/c of the windows cost) and it has been working great so far for my needs (which is basically internet browsing and such, watching DVDs, some GIMP, using emacs and every now and then a word processor, so it's not high end usage). Everything worked right away. Well, I reinstalled an Ubuntu over the trial SuSE Linux version it had out of the box, but I took note in advance of settings and drivers etc. just in case, however Ubuntu 10.10 recognized everything, though it did need some proprietary drivers (for the wireless and I think the video card) and I had to choose a different from default kernel for using all 4GB of my RAM. It also hang once when I chose to download updates during the first installation, but it was fine when I did it in two steps.

The laptop isn't too loud, and it doesn't heat up uncomfortably either. The one downside is that the speakers aren't stereo and not very loud either, though of course you can use earbuds.