RTS2 is project to create an open source environment for control of a fully autonomous observatory. It is running about dozen fully autonomous observatories. Its modular design allow easily addition of new devices (to already huge supported HW list).
Project Galileo at Sourceforge.net aims to provide developers a unique opportunity to develop open source software for an on-line telescope for schools across the UK. See http://www.projectgalileo.org.uk for more details.