I'm surprised nobody here has mentioned the B&N Nook Color. I just recently got a Nook Color ($150 on sale, they're $199 in the store now that the Nook Tablet is coming out) and rooted it to load Cyanogen Mod 7 (CM7) on to it. CM7 is a full blown Gingerbread Android OS with all the same features you would have on a Samsung Tab or Toshiba Thrive. The only thing that those tablets have over the Nook Color, other than being more expensive, is they have a camera and support data network capability (3G/4G/HSPA). I bought my Nook Color specifically for work, such as taking notes in meetings. I have OliveOffice setup with my Google docs so as I take notes they automatically sync with my Google account. Much easier than trying to keep track of paper scribbles everywhere.
It's pretty simple to perform the root and load the hacked OS onto a Nook Color, and then you have a full 7" Android tablet for $200. Personally, I prefer the 7" size over the 10" tablets because its the same size as my notepads I carry around the office, and its just light and simple. I don't feel like I'm walking around with a picture frame.
For what its worth, I also run the same hacked OS on my Samsung Infuse phone, and love it. Makes compatibility between the phone and the tablet very succinct.
For more info on CM7: http://www.cyanogenmod.com/