There are a vast number of knots for ties. The type of knot used changes with time as styles change, and with personal choice. The material type and weight also determine which knot is best. For example, a heavy woven fabric would be greatly oversized with a full Windsor knot.
The typical knots used today are the Half Windsor, the Full (aka, Double) Windsor, the Four in Hand, and the Old Bertie. I typically use the Half Windsor and occasionally the Four in Hand.
Here are a few videos on how to tie various knots.
The above diagrams and others can be found at the Real Men, Real Style website.
Some instructional videos:
The Full Windsor
The Half Windsor
The Old Bertie
The Four in Hand
Kirby Allison has a good video on tying a bow tie.
