Our daughter is about 22 months. We have a newsprint end roll (the unused bit from newspaper printing--available from local newspaper for $4-6 each). She unrolls it whenever she wants and draws. She also enjoys telling her parents what to draw and where. One roll lasts several months. This also taught her how to occupy herself at restaurants (they all have crayons).
We get a lot of use out of Duplo as well. She will tell us she is going to 'play legos' and sit on her floor assembling them. The little people and animals make it a lot more engaging.
