Your two decent options are Seresto or Scalibor. They're both the "new" generation of flea collars that are vastly better than the old, cheap ones. They last several months too, so they're very cost-effective. However, water can effect their usefulness. Also, they need to be snug against the dog (not tight, and definitely not loose) in order to work as designed.
I wouldn't consider any other flea/tick collar -- definitely not any of the cheap-o versions sold at mass retailers.
If you have cats, ask the vet whether these are safe to use with cats around -- I'm honestly not sure about that, as I don't live with them.