also, get this book:
Unix Systems Programming, Kay A. Robbins, Steven Robbins
Prentice Hall PTR, ISBN 0-13-042411-0
the above is superb, in short, it's a must have.
Don't be dissuaded by the title (i.e. i'm no system programmer, i code apps),
if you don't grasp these concepts, please do the world a favour, and refrain
from coding.
the web site for the above book is
http://www.phptr.com
another good book, which covers everything, and is a good intro,
Begining Linux Programming, Neil Matthew, Richard Stones,
Wiley Publishing, Inc., ISBN 0-7645-4497-7
hth
happy gentooing