Yahoo Groups just announced that they will embed new links in HTML emails from subscribed groups. From the notice:
Get one click access to your favorite group features.
If your group updated any content, you can find out from the email.
- Message Archive Read and reply to group messages
- Photos Share photos from your photo album
- Calendar Coordinate group events
- Polls Ask group members what they think
- Links Store and share links to web sites
- Transfer Files Share documents and files
- Database Manage group information