If you do work on your home computers, you can copy files up to the inst machines pretty easily. Just open up a new shell window (Terminal in the Applications folder on a Mac) and do something like this:
scp PATH/TO/FILE.scm cs61a-XX@star.cs.berkeley.edu:~
(in some fonts it may be hard to make out that last character; it's a tilde ~, found at the top left of a standard US keyboard)
This copies the files to your home directory on the inst machines. Make sure you change the underlined parts to match your file and login!
On Mac OS X and some Linux distros, you can actually type scp and a space, then drag your files in from the Finder or other GUI file manager. Then add the last argument (your login and the server, followed by :~. Make sure you put spaces between each argument!)
If you have directories already created in your class account's home folder, you can specify a specific directory to copy into. Just replace the ~ at the end of the last argument with something like ~/proj1.
You can also copy multiple files by listing them all before the last argument (the part with your login and the server).