Google this week unveiled a host of new gadgets that let enterprise Gmail users customize their e-mail experience. The new Gmail contextual gadgets represent a new Gmail API that lets Google Apps Marketplace applications present relevant information to users in their Gmail, when they're reading a message.

Google's launch of Gmail contextual gadgets comes as Microsoft looks to inject new relevance into its Hotmail offering by adding new features and functions in Hotmail to make it a little more, well, Gmail-like. Microsoft's Hotmail, now called Windows Live Hotmail, now enables photo previewing, social networking, video viewing and a host of new inbox functions like conversation view and one-click filtering, make Hotmail a little more like Gmail, which recently has become the free Web-mail of choice for many.

But as Chandrashekar Raghavan, Google apps extensions product manager said in a blog post: "Contextual gadgets in Gmail – like YouTube, Google Docs and Picasa previews – intelligently display relevant information from other systems as you read your email, so you can be more efficient without leaving your inbox." Google was also quick to point out that Gmail contextual gadgets are available now, while Microsoft's Hotmail updates won't start reaching users until June.

Here we look at 10 Gmail contextual gadgets and what they do.