One year ago, Network World highlighted 10 open source companies on the rise in such diverse fields as storage, VOIP, systems management, virtualization and the use of software to aid disaster relief.

Read on to find out why we named these vendors "Companies to Watch" last year, and get updated on where they are today.

1. Cleversafe

Why it made the list: As companies start taking a closer look at building grids, Cleversafe provides an open source platform to serve as the foundation for commercial, dispersed storage grids that provide secure storage because data components are scrambled and stored in separate locations.

Highlights from the past year: Cleversafe is trying to build a so-called "storage Internet" and is testing the idea with multiple hosting and access providers that are contributing storage servers and bandwidth. "Our focus for the past year has been enhancing our technology to support the scale required to store the world's data," says Chairman and CTO Chris Gladwin.

2. Digium

Why it made the list: The open source Asterisk software is making it easier and more cost-effective for companies to launch VoIP projects. "What Digium can do for telephony is incredibly powerful and disruptive," says David Skok, a general partner at Matrix Partners.

Highlights from the past year: Digium is building new headquarters in Huntsville, Alabama. The company says its software is being used in 140 countries, with two million servers running Digium's open source telephony platform.

3. Hyperic

Why it made the list: Application and Web monitoring from such big vendors such as CA, IBM and BMC Software can be bulky, complex and difficult to deploy. Hyperic takes a different approach to Web infrastructure management and has created a simpler tool that lets IT managers monitor commercial and open source technologies from a single portal.

Highlights from the past year: Hyperic won the Best Systems Management Tool product excellence award at LinuxWorld this summer. In June, Hyperic secured US$6.1 million in venture capital funding.

4. Optaros

Why it made the list: Optaros, which provides consulting and systems integration services focused on open source software, can be the guiding hand for enterprises considering using open source to solve business problems. It helps customers determine where open source makes the most sense and helps put together open source components to create platforms for business.

Highlights from the past year: Optaros released an online catalogue of open source projects to help IT managers find the best free software. Of more than 140,000 open source applications available, Optaros selected 262 projects that are enterprise-ready. Optaros also secured US$13 million in funding last November.

5. Qlusters

Why it made the list: The number of open source systems-management vendors is growing, and Qlusters' product, openQRM, has proved its worth in commercial deployments. The open source platform benefits enterprise customers by offering plug-ins that let the platform hook into existing systems, whether open source, proprietary or internally developed.

Highlights from the past year: Qlusters raised US$10.36 million in funding this summer, bringing its total to US$33 million.