Refrigerant
If you have an '00 model car, chances are that some of your A/C refrigerant has slowly leaked out during the past seven years. Your Civic should have R-134a in its A/C sytem, since most every US-market car built after 1993 uses this type of refrigerant.
R-134a replaced R-12 {known to most of us as 'Freon'}, which is almost impossible to find anymore. You also must have EPA certification to purchase R-12 nowadays.
The good news is that R-134a is relatively inexpensive and you can buy it at any auto parts store without having EPA certification (unlike R-12). Wal-Mart sells a recharge kit for about fifteen bucks, which lets you recharge your system in your own driveway without any special equipment.
I have never used one of these kits, but I know they sold quite a few of them at Wal-Mart. The shelves were full of them about a month ago, and they only had about a dozen cans left as of yesterday. Paying $15 and doing it yourself beats the heck out of paying $100+ for a shop to do it; that's for sure!
According to the directions, you run your car until it reaches operating temperature, crank the A/C to "MAX" and then attach the recharge kit's hose to the low-pressure valve of your A/C sytem. Fill it until the gauge registers the proper pressure in the green zone and then it is done.
Provided you have no other defects with your A/C system, you should be cool the rest of the summer. Even if you have a minor leak somewhere, I reckon it is more economical to buy a can of it once or twice a year than to spend a few C-notes for a mechanic to diagnose, 'dye test' and re-pressurize your entire system.
Let us know how it works!