http://runescape.wikia.com/wiki/RuneScape_Wiki
Click the link above and search for any monster you want to know drop rates for (eventually I will have every item listed, but this is a temporary solution).
Common: 100%
Uncommon: 30% (3/10)
Rare: 2.7% (1/37)
Very Rare: .35% (1/286)
Ultra Rare: .2
