This site explains the basics of writing assembly programs in Linux as well as pointing out some differences between Linux and DOS assembly.
This table contains a more up to date and complete list of the Linux kernel interrupts (inx 0×80) and their usage.
This table consists of all the Linux kernel interrupts (int 0×80), their arguments, and their purposes. It is written for kernel version 2.2 and as such is a little dated.
This site explains all the basics of x86 assembly: memory management, arithmetic, conditional branching and subroutines.