It’s easy to focus on SaaS companies in the enterprise space, relegating on premise to a wheezing and gasping dinosaur in it’s final days, but the fact remains that on premise software remains the overwhelming majority of spend for enterprise IT and that’s not likely to change for a few more generations.
Open source has been a bigger disrupter to enterprise IT than on demand SaaS but because it tends to focus on IT needs rather than business user needs, it gets much less attention. While open source for enterprise business applications has moved up the food chain more slowly than I predicted, it is happening and in the coming years we will see traditional proprietary code vendors come under assault once again by the prospect of open source, this time resulting in more significant progress than in years past.
Other open source companies I like:
Zenoss: Network and system monitoring software.
Enomalism: Build your own private elastic compute cloud.
rPath: Virtual appliances.
OpenAir: Project management software for professional service organizations.