Baen Free Library

If you're looking for good series check out the Dahak, Honor Harrington, Legacy of the Alldenata, Lt. Leary, March Upcountry, Starfire, and Vorkosigan Saga series (sp? what's the plural of series)

If you can find a copy, At All Cost by David Weber has a CD with a lot of his works in various formats. Baen has done this a couple of times with his works along with several other authors.