mac needed things

My officemate wanted to send me a large data file today, but neither of us had brought our USB drives. (I bought my 2Gb drive from YeahDone which has the cheapest USB drives in Australia - pity it's not on any of the search engines like StaticIce.) So she compressed it with 7-Zip which happened to be on her desktop... briefly confusing me. I browsed maximum compression wondering what the best compression program for the Mac is, but realised I have lost interest in the subject a bit. I just have so much storage now. A 120Gb notebook drive for my Powerbook is only about $400... the only other thing I'm thinking of buying is a PC card with four USB 2.0 ports. $22.20 at the moment.