Here is some information for people who are trying to get published, or are seriously considering it.
Thumbs Down Agency List – The Science Fiction and Fantasy Writers of America (SFWA) website maintains this list of known scammer agencies (it’s by no means an exhaustive list, but it’s a good place to start). They also provide a list of things a reputable agency will not do (i.e. charge you an upfront fee for representation).
Here is an informal survey of sci-fi and fantasy writers and the average advance they receive when they sell a book, and how many sell a book with and without an agent. (I’ll throw in a spoiler: people with agents tend to receive, on average, higher advances.
Writer Beware: Learning the Ropes – How best to research the agent/publishing market in order to avoid being scammed.
Science Fiction, Horror and Fantasy Book Publishers – A list of publishers–large and small, print and electronic, novel and magazine–who publish these genres. You will probably do better financially with a large publisher, but you’re probably more likely to get a response from a small publisher. Of course you need to be prepared to do a lot of your own marketing (or get an agent that is serious about handling that), but you will probably need to do more with a small publisher.
On a lot of publishers’ websites, you will have to do some serious digging to find out if they accept queries direct from authors. And before you get your hopes up, a lot of publishers won’t accept from an unagented author (especially true of large publishers; less true of small ones).