Framework /starting Point For Social Networking Site In .NET?

I'm an ASP.NET/SQL Server developer and would like to develop a (intially) basic social networking site (gasp). Before I start from scratch with a blank solution in ASP.NET, I'm wondering if there are any frameworks out there ASP.NET specific that would serve as a good starting point. I'm already thinking of using the Google Maps jquery control for my Google Maps integration, as well as the 'sharethis' control for my social networking website sharing integration. Captcha for human authentication... But other than that I'm not sure what I can leverage... Nothing on Google jumped out at me on my search terms.

I'm also wondering if anyone else has done something similar and could share their post mortem/war stories with me.

I'm also open to learning a new platform/language if it would mean saving time - my experience is mostly in ASP.NET, so that is what I plan on using if it makes the most sense. My initial requirements are basic and realistic - profile setup (images, information, etc.), 'group' creation, Google Map integration, calendar controls shared by groups, SMS support, discussion forums among groups, searching for groups, OpenID integration most likely, etc. I am not going to try to build the entire site and then release it, but take baby steps and release pieces of functionality at a time.

EDIT: I've found DotNetOpenAuth which seems to be a nice API for handling OpenID for ASP.NET web forms. They also have an ASP.NET MVC version

EDIT2: I also found MS Web Platform. This looks like some good stuff. Anyone ever use it and think it would do well for this sort of app?

EDIT3: I found a library for DotNetNuke called ActiveSocial. It's priced right ($500) and has more than the features I need but lacks some. I wonder if anyone here has ever used AS before. Is DNN easy to extend so I can add Google Maps functionality and such? It doesn't say anywhere on snowcovered (the vendor that sells AS) if AS comes with the source. If it didn't, then I might be screwed because I wouldn't be able to integrate the functionality I want..