Mountain Biking - Component Upgrade

I have an Aluminum Trek 820 (1999 I believe) with a Manitou Pro front fork and i want to try to reduce the weight of the bike. I don't really want to get a new bike, I would rather upgrade the one that I have. will new front/rear derailleurs, crankset, shift/brake levers, cassette make any real diffrence in the weight or is it just a waste of money? If it is not worth it, are there any opinions on a new bike in 500-800 range? I would be looking for something pretty much just like my 820 but lighter and with better components. Any ideas?

I have an Aluminum Trek 820 (1999 I believe) with a Manitou Pro front fork and i want to try to reduce the weight of the bike. I don't really want to get a new bike, I would rather upgrade the one that I have. will new front/rear derailleurs, crankset, shift/brake levers, cassette make any real diffrence in the weight or is it just a waste of money? If it is not worth it, are there any opinions on a new bike in 500-800 range? I would be looking for something pretty much just like my 820 but lighter and with better components. Any ideas?
The amount that you will spend on new components for that bike would be better spent on a new bike. Other areas to consider - wheelset, stem, seatpost, handlebars and fork. How many MM's of travel does your current fork have?

My fork has 100mm of travel. It seems like a lot of the weight is in the fork. which upgrades will give the greatest weight reduction?

like Raiyn said, the cost of upgrading all of this is practicly the value of the bike. You can go the route i did and just upgrade every component on there and eventually, the frame itself so you reach the point where you have a new custom all together.
The best place to save weight is the wheels. From what i see, many derailleurs out there are within +/-50 grams out there. For example, i think my x.7 (40 bucks) is 270. The x.9 for a little more is 20 grams less and the x.0 for 100 more is around 200.
the Sram 990 cassette is 35-50 dollars, and only a few grams more than the XT cassette but quite a bit less. Shifters i have found to all weight in similar to eachother.

My fork has 100mm of travel. It seems like a lot of the weight is in the fork. which upgrades will give the greatest weight reduction?
Are you planning on racing or something? In which case you probably would want a new bike rather that relying on a 6 year old aluminum frame.

The greatest weight reduction comes from....
Wheels
Fork
Frame

No racing, just daily commuting. I ride at least 15 miles a day and I feel as though my bike is a little sluggish. I want it to go faster and smoother so my commute takes less time. I ride through ciry streets hopping up and down curbs.

what are some light wheels that arn't really expensive?

well really light and cheap are not compatible. How much are you willing to spend?

Cheap
Light
Strong

Pick TWO

I have around 500 to spend on all of my upgrades.

I'm not the lightest person so I probably would need something strong. I don't have loads of money ($500 for all upgrades) but I would like something light.

I have around 500 to spend on all of my upgrades.
What you could do is save for a new bike that you can upgrade for use out on the trails and swap the components that you take off the trailbike onto the commuter thereby upgrading two bikes for the cost of upgrading one.

This is what I did http://www.bikeforums.net/showthread.php?p=545760#post545760
there's a link to the commuter bike as well in that post

I'm not the lightest person so I probably would need something strong. I don't have loads of money ($500 for all upgrades) but I would like something light.
Nor am I, perhaps you could look through my choices to see what rings bells for you

any thoughts on the Mavic 717 with the xt hubs?

any thoughts on the Mavic 717 with the xt hubs?
the 717 is a nice rim. I avoid mavic usually because i think Sun and velocity are a far better buy. ALso, though the XT is a fine hub you will be better off going for JuJus if you ask me. THey have cartridge bearings and are not much more. If you go to Sun rims you can easily afford them for that price

Are you running slicks?

If you're using knobbies on pavement, thats a MAJOR slowdown.

any thoughts on the Mavic 717 with the xt hubs?
Good wheel but overkill on a commuter

Are you running slicks?

If you're using knobbies on pavement, thats a MAJOR slowdown.

I have Nimbus Armidillos. They are great.

I have Nimbus Armidillos. They are great.
Indeed they are. :D