The best collaboration technologies immediately fit into the flow of your work and improve or streamline it in some way. I've been running Rapportive, a Firefox or Chrome plugin that displays useful contextual information next to your gMail for a month and found it extremely useful.
The English founders put up a website to showcase their technology for funding partners and quickly saw users jump on the service which is similar to Xobni, the Microsoft Outlook add on. The Rapportive team are in San Francisco talking to VC's and a couple of them took a few minutes to discuss their product and plans with me this afternoon in the video above.
Essentially, once Rapportive is installed and activated any email you open will be augmented by a right side browser pane pulling in information from a variety of sources to flesh out additional information about the sender (hover over other recipient email addresses to see their info). You typically see a mugshot and profile information pulled from a variety of sites: LinkedIn, FaceBook, MySpace, Friendster, Flickr etc (also with links to their profiles), recent tweets and Twitter name and a CRM style text field to make notes.
I've found this extremely useful - like Reframeit, which is useful for marking up and sharing information on web pages, Rapportive augments your work patterns and takes several steps out researching someone whose email has intrigued you.
The plugin hasn't slowed my browser down at all and it's also useful for checking what profile information is dredged up (my age of 99 years old was from an ancient MySpace account. Rapportive have recently turned off revealing age).
It's not clear what Google will be doing longer term with relationship management but this free plug in has been working like a charm for me.