the Google Groups team launched a new beta version of Google Groups at groups-beta.google.com with a completely new design for individual groups. Group owners can now create a welcome message, upload a group logo and customize your fonts and colors. The Pages feature lets you create web pages inside your group, and work on them with others.

Other improvements to Groups include:

Using Gmail’s message cards for discussions, which makes them easier to follow
Adding a Files section so users can share and collaborate on documents
Helping groups have a better sense of their members with the Member area

Via Google Blog