You already know uno to venti. The tens up to a hundred are:

20 venti	30 trenta	40 quaranta	50 cinquanta
60 sessanta	70 settanta	80 ottanta	90 novanta
100 cento

From trenta on, they all end in -anta — handy for spotting them in fast speech. Watch sessanta (60) and settanta (70): one has ss, the other tt, and they're easy to mix up.