For Linux, the Unleashed books (Sams publishing) seem to be pretty decent. Specifically - Debian Unleashed. If you haven't dug that far into it yet, the empeg runs the Debian flavor of Linux.

For C, I've been reading GNU C++ for Linux, by Tom Swan. This covers the free C++ that comes with most Linux distributions, from the ground up.

Not sure what veteren Linux gurus and/or seasoned programmers have to say about either book, but so far, they've done me pretty well...