Raspberry Pi ($25 Linux Box)

Must of the students who have ever tried to use any variety of micro-controllers should be aware of the problems and the time needed to setup and run even the simplest board. Now however there exists a board which has linux on-board! It can be connected to a monitor with an HDMI connector and manage any hardware you have through a USB interface, and all in one for just $25!

There is even a version of the board with built-in network adapter! this video can't for sure, show even the slightest possibilities this board brings to life but will just make you more impatient to get your hands on one of them:

Unfortunately you have to still wait for the real sale to begin, they have just entered the production in less than a week ago, so be patient.  Here is the website of the project and the company: raspberrypi.org