I didn't read the other replies but here are some good upgrades:
Barrel- if you really want to increase your accuracy then a high quality barrel is a must have
Stock replacement- most factory stocks are crap besides the 700P police stocks, HS precision and McMillan make great stocks.
Stock bedding and free floating the stock- this is a very cheap and easy to do mod that you can do at home and provides good results for the price, can be done with your factory stock or with aftermarket stocks
Trigger- don't bother with the factory trigger, go with an aftermarket trigger like Timney. Expect to spend around $150 but with a complete replacement trigger you can install it yourself at home, you would pay at least half of that to have a gunsmith do work to your factory trigger and it still wouldn't be as good
Base, rings, scope- this is VERY important for good accuracy. You can have a $3000 rifle that is capable of 1/4" MOA groups but without good optics, base, and rings you will NEVER shoot anywhere near what your rifle is capable of
Gunsmithing- you can have your action/bolt trued/blueprinted
I am sitting in class right now so i did not go into much detail on most the options, if you want more info on any of it shoot me a pm and i'll be glad to answer your questions