OpenCongress.org brings many of the tools of social networks - blogging, comments, syndication, interest rankings, tagging, and so forth - to the process of actually creating the laws themselves.
Although the OpenCongress site is not in dot-gov, it is definitely about dot-gov and really packs alot of citizen participation in one space.
For instance, the web designers of OpenCongress.org used one particularly innovative extension of commenting systems to make it possible to post bills that had come out of committee, and to allow people to comment not just on the bill overall, but even on specific provisions within those bills. It is perhaps debatable whether the comments themselves make that much of a difference - though I did read a couple that made me see some sense in an alternative viewpoint - but the very fact that the commentary exists in the first place means that people are reading the bills, and beginning to understand a process that, for the most part, has usually been something that took place in the background. [emphasis mine] -- Read more at O'Reilly.
People can easily find a bill, see what is popular (by views, blogged, press coverage and search terms!), and provide feedback. The site includes an A to Z issue index and a list of Congressional Committees and their relationships with links to additional committee information--like who is on the committee and what they are doing.
Yes, much of this information is available on House and Senate sites, but OpenCongress.org provides the relationships and context outside of the individual member or committee structure. You can even rate your Senator or Representative. Now that is interaction that you are not likely to see on an "official" Congressional site.
Why? It's hard for a site owner to be critical of themselves or to open themselves up for criticism (or insult). Every week there is an agency conversation that ends with, "Well, we can't take comments because someone might say something bad." We are just starting to see agencies taking this risk, like the TSA Checkpoint Blog*.
I think that the features on OpenCongress.org deserve a close look. There is much that government could model to invite participation and increase transparency--from the friendly interface that puts participation front and center to the variety of intuitive ways to get to the information you want to the ability to subscribe for updates in different ways.
[* Disclosure: I have a professional relationship with TSA. But I would still think that their efforts in blogging are brave and spot-on!]