If you subscribe to the group, then you can click on the tab "My subscriptions" and the newest posts will show up. I think this is a very neat feature!
As far as categorizing them, the only way I can think of is to create a number of "sub groups". I am not sure this is possible, and, if it is, I think this might end up being more trouble than it is worth. This would entail having the members click down to the appropriate sub group for each new thread posting.
This group is not that active, so, IMO, I don't think it is necessary to separate topics.