Storage has always been a point of contention for the Xbox 360- the console came in a variety of configurations with on board hard drives, but it only used proprietary formats, meaning only (pricey) official hard drives were supported, and even they were capped out at a few hundred GB.
And while some will argue that it is now too late, what with the Xbox 360’s successor now being on the market, it is still about to change- a new system update for the Xbox 360 will allow users to connect hard drives as big as 2TB via USB and use them to store data. Up to two will be supported at a time, and Microsoft will no longer reserve any space on your hard drive beyond what the data already takes.
To people who are part of the Xbox 360 Preview Program, this update is now already out and available- to others, it will be rolled out later this year. As always, do note that some hards drives may not be supported.