We counted to 89 in ASL, let's keep going!
To do the sign for 90, make the hand sign for 9, holding your pointer finger down with your thumb, and your other fingers up, with your palm facing away from you.
Then close your fingers together all pointed forward away from you, for zero.
For 91 through 99, just do the sign for 9, and then the sign for the number 1-9.
Here is a helpful video to show how these signs are done.
ASL Numbers 30-100 in Sign Language - My Smart Hands
(from: wikipedia - american sign language)
Italian: novanta, novantuno, novantadoue, novantatre, novantaquattro, novantacinque, novantasei, novantasette, novantotto, novantanove
German: neunzig, einundneunzig, zweiundneunzig, dreiundneunzig, vierundneunzig, fünfundneunzig, sechsundneunzig, siebenundneunzig, achtundneunzig, neunundneunzig
Spanish: noventa, noventa y uno, noventa y dos, noventa y tres, noventa y cuatro, noventa y cinco, noventa y seis, noventa y siete, noventa y ocho, noventa y nueve
French: quatre-vingts dix, quatre-vingt onze, quatre-vingt douze, quatre-vingt treize, quatre-vingt quatorze, quatre-vingt quinze, quatre-vingt seize, quatre-vingt dix sept, quatre-vingt dix huit, quatre-vingt dix neuf