nerys -- If you like the sort of stuff they offer,
Baen offers a lot of their titles as DRM-free files in several formats (including RTF, my personal favorite for the Reader), and their prices are quite reasonable -- I don't think there are any single books for more than $6, and they offer a monthly bundle (webscription) of about 5 books for $15, any of which you can buy or not at any time.