Here's a fun weekend project for those of your who like building your own Mac add-ons. The raymii.org site has posted a tutorial on how to build your own US$35 Time Capsule using a Raspberry Pi single-board computer, rather than paying $299 for the official Apple version (that is, if you happen to have 2 TB of hard drive storage kicking about unused). Apple's Time Capsule bundles an Airport wireless router with either 2 TB or 3 TB of internal storage, to back up multiple Macs on your network.
For the project, you'll need two things; a Raspberry Pi, Model B/B+ and a USB disk. The builder has tested this method with a 128 GB USB flash disk and a 1 TB USB hard drive. It's possible to get a lot of storage using this method. The entire process is complicated, so set aside a good block of time to complete the project. [Also, don't forget to test your backups! --Ed.]
Once you're done, you'll have a perfectly serviceable budget Time Capsule. Enjoy the storage and savings.