What kind of $$ are you willing to spend?
I know this is no place to start, but your question reminded me of this site and the goodies it has:
http://www.chevrolet.com/performance/crate-engines.html
How about this engine in your hoe?
For some real advice, start with what your budget can bear.
For a coolness factor, you may want to start with what is obvious on the outside. Wheels, tires and lowering kit/shocks, sway bars, adjustable panhard - just these things alone can cost you $3K+ or so depending on what you want.
Those items mentioned by Josue above are also things many choose to do to their truck for some minor power upgrades. Free flowing, big valve heads could get you some more power, but you're talking $$ and surgery.
http://www.chevrolet.com/performance/components.html
If you need a sound system, this is also something that can cost, but you can break it up into small chunks of money and get results you can literally hear.
Have fun and keep us posted (with photos) on what you do. You need to get some photos up anyway so we know what you're starting with.
Joe