You main resource for Linux/Unix assembly programming material is Linux Assembly :).
Here are some resources listed there.
If you're are interested in Linux/UNIX assembly programming (or have questions, or are just curious) I especially invite you to join Linux assembly programming mailing list.
This is an open discussion of assembly programming under Linux, FreeBSD, BeOS, or any other UNIX/POSIX like OS; also it is not limited to x86 assembly (Alpha, Sparc, PPC and other hackers are welcome too!).
List address is mailto:linux-assembly@egroups.com.
To subscribe send a blank message to mailto:linux-assembly@egroups.com.
List archives are available at http://www.egroups.com/list/linux-assembly/.
Unfortunately there are no ready books I can recommend on the topic. However I'm in the progress of writing a book "Linux Assembly Programming", which /hopefully/ will be published somewhere in 2000.
Note: if you know any Linux/UNIX assembly
related project/webpage
not mentioned here, please send me the url.