Looking to try a new series but aren't sure it'll be worth it? The Baen Free Library has a collection of science fiction and fantasy novels by authors such as Mercedes Lackey, Larry Niven, Elizabeth Moon and others. Heavier on the SF than on the fantasy, although someone mentioning it having Moon's Sheepfarmer's Daughter was what alerted me to the site's existance.
The concept behind the Library is to introduce readers to authors they may not know and, hopefully, gain new customers as the readers purchase the remaining books to find out what else happens in the series. To that end, the novels are almost exclusively parts of either a trilogy or a series (either complete or ongoing) as opposed to "stand alone" books. You can read the rest of the thoughts behind the idea on the site itself.
Anyway, all the novels are complete and free to be downloaded or read online. It seems like a great way to test drive a few new authors without investing in a series that may be (to you) a dud.
Edited, Dec 19th 2006 10:05pm by Jophiel