Firoz points to some very nice "cheat sheet" pages for ASP.NET developers located here:

JavaScript Cheat Sheet
CSS Cheat Sheet
HTML Character Entities Cheat Sheet
MySQL Cheat Sheet

They are ready to be printed and mounted up on the wall.

 

Speaking of which, I received a copy of the VisiBone Browser book for web designers:

 and it's really really nice. After a short usage period by one of my web-dev friends, they seemed to really like it. Think of it really as a bunch of cheat sheets mounted together, printed and wrapped, ready for putting up on the wall. It contains the following cheat sheets: Colors (Visible color charts), Fonts and characters, HTML and XHTML tags, CSS Styles, JavaScript, DOM reference and regular expressions reference.

The nice thing about it is that all the references are color coded so that you know, for example, which tags are available only for IE< or which tags are not supported by Mozilla and Netscape browsers.

I'd recommend it, even though the price is a bit steep, since it's of really high quality, and to be used sort of a "buy once, hang forever" on the wall kind of thing.