I have the following computers right now:

Dell XPS M1330 laptop
This is a pretty good computer: light, powerful, and not too big 
(although a little pricey...no machine is perfect).  I prefer a 
12 inch screen, but compromised a little with the 13 inch screen 
on this computer.
I wiped the hard drive and installed ubuntu linux, freebsd, and 
left room for one more operating system (I probably will install
slackware linux, but will keep looking for an os that is *nix,
but is sufficiently different from the other two oses I have so 
far).  I only just installed freebsd and still need to do some 
modifications: wireless and x windows do not work yet due to
the hardware (Broadcom BCM4315M wireless and Nvidia display).

OLPC XO-1
I got the One Laptop Per Child (OLPC) model XO-1 laptop during
the give-one-get-one program at the end of 2007.  It runs a
customized version of fedora linux with OLPC's "Sugar" interface.
It is good for reading ebooks, browsing the web, and playing
educational games (it was meant as a teaching tool).  It uses 
very little power.  It is durable (meant to be used in the 3rd
world), so it is great to use outdoors.  The OLPC foundation has 
been far less successful than I and many people hoped, but the 
dream is not dead yet.

Nokia N810
I used a Psion series 5 pocket computer years ago and loved it.
After I broke the screen, I looked for another good pocket computer, 
this time with hightened expectations (wanting a more robust online 
experience than the Psion could offer).
The Nokia N810 is a good fit for me.  It is pretty good at surfing 
the web.  I can whip it out and type out a note with the built-in 
keyboard, without waiting for it to boot up (previously, I was 
tempted by the Nokia 770 and N800, but I held out for a keyboard,
no matter how small).  It runs Maemo's distribution of linux, with 
the busybox shell (bash can be added).  In addition, the speakers 
are better than many laptops, so it is good for music too.