A list of online resources. This is only a small sample, of course, but tends to reflect my interests.

Computer Science Books Online

Some Computer Science books online.

ACM

The ACM web site. The ACM is the pre-eminent computer science and computing professional organization.

IEEE

The Institute for Electrical and Electronic Engineers. Just like it says.

Computing Reviews

Reviews of articles, books and other computer oriented literature.

Haskell

All about the programming language Haskell.

java

Sun's Java site.

citeseer

Online citation tracking and paper information (often the papers in Postscript or PDF format) in the computing literature.

Lambda the Ultimate

Programming language blog.

Linux books online

Some free Linux (many also cover Unix in general) books online. 

On Learning Systems

A very nice blog post about how you learn, and in particular, about how you learn about software systems (languages, APIs...)