How big is the blockchain on disk as of 5th July 2012? I just started Bitcoin-qt for the first time, and it is syncing. How much space does the blockchain take up? I have my drive heavily partitioned, and my /home partition (linux mint) is only about 20GB. Does anyone have a size accurate within 100MB?
At the moment, it's about 2.6GB, but it will be growing with time.

You can try looking into using an eWallet or some lightweight clients if you are tight on the disc space. Their space requirement is minimal in comparison, but the security model they offer is different. The lightweight clients are developed by other people than the core Bitcoin team, so you have to know that you can trust them (haven't yet heard about a case of the lightweight clients being malicious). With the eWallets you put the security of your money in the hands of the third party and their server. There have been incidents of people losing a lot of coins because of this (like MyBitcoin), but if ran well and by trustworthy people, your Bitcoins can be more secure than on your computer.