Since we moved our mails and calendars to Google Apps a few weeks ago, we're also starting to use the Google Groups feature more. It's great that we can use it for our internal mailinglists and everyone can set new ones up easily.
But those private Google Groups have one big disadvantage, they don't provide an RSS feed like the public ones (eg. for webtuesday-announce). Actually they are provided, so if you go to something like https://groups.google.com/a/example.org/group/somelist/feeds, you see all the feeds and they show up in your browser. But as soon as you try to access them outside of your logged in browser session, it doesn't work, there is no way to somehow provide your credentials.
That's too bad, since we wanted an RSS feed to try out some ideas and we almost already started to implement some not-so-elegant ways to get this. But then I remembered using playnice by Andy Blyler, which did a google login to Google Latitude to update my current position (taken from Find-My-iPhone in Mobile Me). It does this with using the COOKIEFILE option in PHP's curl, which stores all the cookies a HTTP requests sets and emulates a login on the Google services.
I then just made it use the Google Groups login page instead of the Google Latitude and called the RSS url and it actually worked.
As I'm certainly not the only one which misses that feature (according to a google search, I'm pretty sure), I published the whole thing over at github as GoogleGroups2Rss. Have fun with it and make sure that script is properly secured, otherwise anyone can read your internal mailinglists :)