I usually offer to keep the kids (if they have any) for a little while, so they can rest or go to the dr, etc. And I usually prepare a meal or two for them and their families. Sometimes, depending how close a friend it is, if I'm out & about, I'll pick up a fresh bouquet of flowers, or a few things from the store, just to lighten their load.
MIL is sick right now, and lives about 30 minutes away. It's killing me right now to not be able to get to her, and make her some soup or get her some tea or pop. The 1 1/2" thick ice on our driveway and most of the back roads is making that impossible for me right now, and it's driving me bonkers!!