Now a big name in the music business, Musician's Friend was founded in 1983 by Robert and Deanna Eastman, and has since become a huge music gear marketer. They operate a website at Musiciansfriend.com, from which you can request a free catalogue, or simply browse through the products online.
Musician's Friend stocks guitars, basses, keyboards, percussion, amps, DJ gear, recording gear, and more. They have an excellent selection and reputation. The prices they advertise are very reasonable, and generally reflect the price at which you can find that gear anywhere. Many music stores actually use MF's catalogue as a basis from which to set in-store prices.
If you are a musician planning on buying new equipment, consider checking out Musician's Friend to see what gear is avaliable, and the maximum price you should be paying for it.