A lot. Wikipedia lists 64.
Japanese particles - Wikipedia, the free encyclopedia
Asking someone to tell you a little about them is like asking people to tell someone about prepositions in English. You can't tell "just a little." You can tell entire books. The link I provided above will be better than any post you'll get in response to your very broad, general question. You could ask more specific questions here and get answers, though!
A few of these books are useful:
Amazon.com: all about japanese particles