Here are various calculators for Jewish learning.

Daf Yomi Bavli Find the Babylonian Talmud reading for any valid date.

Daf Yomi Yerushalmi Find the Jerusalem Talmud reading for any valid date (now corrected to agree with the official schedule maintained in Jerusalem).

Mishnah Yomit Find the Mishnaot to learn for any valid date.

The Yomilator A downloadable Yomi calculator for the Palm; calculates the three Yomit listed above for any desired date. (Bugs were recently corrected in the Mishnah Yomit and Yerushalmi calculations; however the program may still be incompatible with Treos; hopefully this will eventually be fixed.)