With Windows 7, can I set up more than 1 HomeGroup on my laptop? i.e. 1 at office and 1 at home.

Can I belong to multiple HomeGroups?

You can leave a HomeGroup to join another one, but you may participate in only one HomeGroup at a time. This configuration makes sense because you will likely share items on only one home network at a time. Writing down the password for each HomeGroup you wish to participate in will allow you to leave and rejoin each group as needed. This way, if you are visiting another home network (other than your own) you can access printers and other resources there. Simply choose to leave the HomeGroup you belong to and join the new group.

Note: When you leave a HomeGroup, all connections and access to resources shared to that group will be disconnected and need to be reconnected when rejoining the group.

Source: TechRepublic

Have a look at this discussion thread @ sevenforums.