Dragos (from @rgumente) had a nice blog entry summarizing some sites that give us sneak previews of some future projects currently being undertaken by Google, Microsoft and Yahoo.

The Google Labs site was pretty interesting, and I would highlight Google Scholar (searches through journal articles and other scholarly literature), Google SMS (what about pushing the answers to your cell phone via SMS?), Google Video (search through TV programs online, but the actual videos are not yet captured - instead, you get some snapshot pictures of the show with descriptions) and Google Suggest (this one is pretty interesting, with Google offering suggestions in real time as a user enters his/her search).

Microsoft's MSN Sandbox is one of their many sites devoted to offering a glance into some projects that they are currently engaged in.  I would also suggest Robert Scoble's own blog (Scobleizer), and MSDN Channel 9.  The Sandbox site offers an RSS feed, and its main highlights are an AntiSpyware tool, MSN Newsbot (an automated news service that updates users continuously on stories reported online, even suggesting related stories), and MSN Spaces (which was discussed here before).

Last but not least, Yahoo has a Yahoo! Next site devoted to future technologies, and the apps that caught my eye included Y!Q Beta (contextual search engine) and Yahoo! Travel FareChase Beta (searches through various travel sites across the web to find the cheapest fares).