So, I thought a little wrap up of what we’ve seen and how I figured all this out. Much of what we’ve looked it is just a simplified version of the standard ‘People and Groups’ pages, and a lot of digging around with reflector was involved!
We’ve seen:
- That listing users is fairly simple using some ‘magic values’, but that supporting the ‘View Selector’ is a bit more complex!
- That resolving the MembershipGroupId GET parameter is important, but pretty simple, and that there are many ways you could choose to do this.
- That adding users is pretty simple too – it’s just the sort of SharePoint API code you’d get asked about in the WSS3 App Dev exam.
- That removing users is a bit yucky – JavaScript to get the IDs of selected users – but again, the code itself is pretty straightforward.
Now the moment you’ve been waiting for – the code for the 3 pages we’ve used itself. Note that I’ve also used a custom Master page for my sites – you’ll want to build your own, with your own navigation, etc..
Andy Burns' Blog 
Thank you for taking the time to share how you did this customization. The permissions situation in SharePoint is one of the most confusing things to users at my organization, and the default interface doesn’t help make it easier at all.
No, I agree entirely – the out of the box permissions UI is deeply confusing.
It’s a bit fiddly, but I hope that this series showed a way of building a simpler interface, which might be useful – though you’d have to consider it in the context of the application you’re building.
Hope it helped!