Comment by URSpider94

Check out http://www.realknots.com/knots/ for a more thorough list. On my short list, I would recommend:

-- the bowline, for putting a slip-free loop around something -- two half hitches, for putting a cinching loop around something -- the clove hitch, for tying a rope to a pole or other cylindrical object

Start with those three, tied properly, and you can do a lot.