In 2007,we designated more than 90 start-ups as worth watching. After a second look, we picked these 10 as offering what matters most in the enterprise -- agility, seamless integration and pervasive connectivity.

3Leaf Systems

Founded: June 2004

Headquarters: Santa Clara

What it offers: The V-8000 Virtual I/O server, an appliance that converts individual storage and networking interfaces from commodity x86 Windows/Linux servers into a single pool, operating on a 10G fabric.

Why we like it: The appliance makes virtual resources appear to servers as if they are locally attached, with full administrative support for network multipathing, port bonding and trunking. The appliance solves the I/O bottlenecks that occur as enterprises add more virtualized servers. "It's definitely a problem to scale up lots of virtual machines on a cluster and not be able to scale up the I/O at the same time. 3Leaf is addressing this," said John Abbott, chief analyst at The 451 Group in our original profile of the company in August.

Since then, 3Leaf Systems has made solid progress. It signed on a new CEO, B.V. Jagadeesh, founder of Exodus Communications and former CEO of NetScaler. It joined the VMware Community Source program for closer collaboration with VMware on technology development. It launched provisioning software for its V-8000 Virtual I/O device and was named to a few more "best" lists like this one.

How it got its start: 3Leaf was founded to solve such problems as the low reliability and resiliency of I/O spawned by virtualization. To come up with its name, founder Bob Quinn e-mailed company supporters for ideas. Clover Systems (playing off the idea of a shamrock and Quinn's Irish heritage) was one name suggested, and it morphed into 3Leaf Systems.

Management: Quinn, who moved from CEO to CTO and chairman with Jagadeesh's arrival, founded and held executive positions with Network Virtual Systems and iMODL. Other co-founders include Scott Lurndal, who previously founded XML PKI company NanoBiz (acquired by VeriSign) and Isam Akkawi, who held lead technical positions at Unisys, nVidia and others.

Funding: US$32.5 million in two rounds, from Alloy Ventures, Enterprise Partners, Intel Capital and Storm Ventures.

Who uses the product: Savvis, as well as several financial institutions and a number of Fortune 100 companies.

Interesting fact: John Kelley, former McData CEO, is on the board of directors.

Apatar

Founded: February 2007

Headquarters: Chicopee, Massachusetts.

What it offers: Apatar open source software that lets customers integrate information from in-house applications, external data sources and applications hosted on the Web.

Why we like it: The Apatar tools help applications easily share data without programming. By creating a single data stream out of multiple back-end sources, Apatar also can eliminate storage of duplicate data. Since we first profiled Apatar in April, the company has been steadily growing customers and gaining attention for its tools, particularly for legacy CRM/ERP applications. In November, the tools became available on Salesforce.com's AppExchange directory and the same month the company joined the MySQL Enterprise Connection Alliance, a third-party partnership for the popular open source database. These tools have been likened to Yahoo Pipes for the enterprise -- they use a visual interface that lets users drag and drop to build an application. No coding required.