Ravi,
Check the recommended reading section in
Tips, Tricks and Traps.
The University of Virginia page is excellent, don't miss it.
Art of Assembly is a fat download (1426 pages!) but it's legal and free. Unfortunately, some of it refers to 16-bit programming, but registers and instructions are also covered for 32-bit programming, see e.g. 4.6.4 80386 Memory Addressing Modes.
The Intel manuals are the reference, of course, but difficult to digest; see
All opcodes in a handy format for a simpler version.
If you are eager on Windows programming, the Modula page and the Iczelion tutorials are interesting.