Spiceworks, a startup that develops Web-connected social IT management software, has hit a significant milestone today: 1 million users. According to Spiceworks, that means 1 in 5 IT professionals in the world’s SMBs (fewer than 1,000 employees) use Spiceworks.

Spiceworks develops a desktop software suite that helps a company’s IT staff collaborate with each other and manage “everything IT.” The IT management software, which is free and ad-supported, currently helps IT professionals provide services for 34 million workers, manage 56 million computers and devices, and spend $173 billion annually on technology products and services.

The compelling part of Spicework’s software is that it includes a social network for IT pros that they use to help each other out that includes a crowdsourcing troubleshooting platform. Its product roadmap is visible to all members, who can vote on which features they want to see next. The application features a network map that visually shows every computer and network device on a company’s IT network, along with their relationships and bandwidth consumption. Spiceworks also recently added a host of plug-ins and social media widgets, letting users keep track track of alerts, tickets, new software, and new hardware, as well as inventory summaries. And the startup lets users add themes and skins to the desktop, create customized user portals, and lets users drop in news widgets from RSS feeds and social networking widgets for Twitter, Digg, Facebook, and MySpace

Spiceworks says that the rise in user and engagement growth has also doubled the number of advertisers and revenue run rate. Advertisers on the platform include Microsoft, Rackspace, Symantec and Dell. The company just raised $16 million in series C funding early this year.