Used the ID brand kit at Pep Boys for $25 including gauge, fitting, hose and 1lb refrigerant/oil/conditioner. This was on wife's '98 S70 last night.

Her A/C was kind of weak last summer, and turns out when I connected gauge the low side was squarely in the low zone at about 15lbs. Compressor was cycling and not staying on due to low pressure. I put about 3/4 can R-134a in to bring up to 25lb or so and all is happy now, A/C will freeze your nose off. Totally easy and low side port is easy to access. Compressor will run all the time now if you ask it to.

This is in Texas by the way and summers are quite brutal on a weak A/C system. As for people saying "an A/C system should not leak at all so there is something wrong" I call BS - I've owned many cars over the years and once they are 5 years old or more they all benefit from a little recharge every so often. Hey, pressurized gas moleclues have a way of getting out of microscopic holes.