Whether you shoot you're a photographer or DSLR filmmaker you know the value of good lenses. Camera bodies are constantly being updated but a solid lens will last a lifetime.
One of our favorite resources for inexpensive optics is KEH. They sell new gear but also specialize in used and vintage equipment so whether you're looking for modern features like AF or want to try out some older generation kits you can find some screaming deals.
Buying used can be a gamble to some but one great feature of the site are KEH's conservative and accurate quality ratings - everything they sell is rated so you'll know exactly what condition your hardware is in before you purchase.
Our personal favs are the 1980's Nikon primes and CanonFD lenses - solid build quality and optical quality that bests most modern lenses.
Always remember - invest in glass not camera bodies