A cheat sheet, printed out, can be invaluable. Here are a few I've looked at:
Nice and compact, going into good details. It comes in colour, but the wonderful thing is it also comes in Excel format, so I could edit the colours.
It doesn't show the new in 1.3 functions, and doesn't point out the deprecated ones ($.browser and $.boxmodel); I annotated that myself using the "Too Colourful" one below.
This one is nice, fits on one page, already monochrome (though using a light grey for optional parameters, which is hard to read). Does not show the parameters like the my first choice above. It is for jquery 1.4, showing what is new for 1.4; but I also wanted to know what to avoid if I wanted to write a plugin that would work back to 1.2.
2 pages worth, shows what is new in jquery 1.3, and what is deprecated. Uses colour and looked terrible as a b/w print-out. Also, it lists each version of similar functions (such as event handlers), which is why it needs two pages instead of one.