There are many good books about UNIX and Linux. None of them are aimed specifically at ARMLinux but most will nevertheless be helpful. A list of books and ISBNs which we have found helpful is provided in the bibliography.
A number of commercially available books and sample chapters are also available on-line including:
Learning GNU Emacs, Debra Cameron, Bill Rosenblatt, and Eric Raymond, 1565921526, O'Reilly & Associates, 1996.
Debian GNU/Linux Bible, Steve Hunger, Randolph Chung, and Steve Chung, 0764547100, IDG Books Worldwide, 2000.
The TeXbook: A Complete User's Guide to Typesetting with TeX, Donald Knuth, 0201134489, Addison-Wesley, 1998.
LaTeX. A Document Preparation System: User's Guide and Reference Manual, Leslie Lamport, 2nd Edition, 0201529831, Addison-Wesley, 1998.
Sams Teach Yourself GIMP in 24 Hours, Joshua Pruitt and Ramona Pruitt, 0672315092, Sams Publishing, 1999.