EveryCircuit is an application for Android, iOS, and the web that allows you to build and simulate circuits. While it is not free, you are able to try it and build simple circuits for free. It can be helpful for figuring out hard circuits homework problems, or trying to create your own circuits for projects.
GHDL is an open source compiler and simulator for programming in VHDL. While it is unlikely to synthesize an image that can be flashed onto an FPGA, it can be used to at least make sure your code compiles when not on campus.
MinGW (GCC for Windows)
Sometimes you need a C or C++ compiler, but not all computers on campus have one, especially some of the Windows labs. When trying to install MinGW, a C or C++ compiler for Windows, it usually requires administrator privileges; which few computers on campus allow.
Stephan T. Lavavej, one of Microsoft's Visual C++ Standard Template Library developers, created his own distribution of MinGW that does not require administrator permissions to install. Simply extract it anywhere on the computer you're using. If you extract it on a flash drive, and you now have a C and C++ compiler anywhere you go.
The distribution also includes several popular C++ libraries as well, such as Boost.