My wife as an Acer Aspire One, with Windows, and really loves it. Now that our kids are old enough to be spending time on the family computer, she wanted a small, portable machine she could use to basically check her email on, browse her knitting forums, and do some basic word processing. She likes the small size, which basically allows her to easily take it anywhere.

These Acers seem to have a good rep, which is why we went with that brand. And the price was reasonable. You can get them with Linux or Windows. Linux seems like the better deal, but my wife didn't want to learn a new OS, so we went with Windows, and she's perfectly happy with it.