Standard in the MIT inventory is the Roland CAMM-1 GX-24 wide vinyl cutter, it cuts 60 cms wide. Price around € 2000
If 30 cms wide is sufficient, then the SILHOUETTE CAMEO is great for only € 300.
The Cameo2 has USB and an SD card, when you replace the knife blade by a pen, it doubles as a plotter .
The new Cameo3 has a double carriage and bluetooth.
The Silhouette Studio software is extremely friendly and intuitive It is free, not open source and will import .dxf files from any 2D package. Mac + Windows. A $ 50 software upgrade will also directly import .svg files, saving you the conversion from svg to dxf in inkscape. It is a fun thing to take to schools, as it also can print stand alone from an SD-card.
Silhouette also has a smaller cutter, the PORTRAIT, which is a revamped version of their previous SILHOUETTE SD.
It accepts 20 cm wide, A4, and uses the same software: $ 180
An overview of 11 small cutter/plotters can be be found here.
A note of software: most cutters can be addressed open source via Ubuntu – Inkscape – InkCut extension.