Dear penny,
As jane says, by far the most important thing is to literally "be there", physically, and able to help with chores and tasks so as to lighten some of the burden at this time.
I think the reason we all feel so awfully useless when we try to find words of comfort, is that we realize that there are no words that bring comfort in these early stages of grief, and we overestimate what we think we ought to be doing. Because we can't think of those myuthiccal magical words that'll make everything feel fine, we may even avoid the person, embarassed because we lack those lovely things to say. In fact, we need say little more than -- "I feel terrible that you are so sad, and wish there was so much more I could do. If at any time there is anything practical I can do to help, tell me and I'll see to it. " And spend time with them, allowing them to be silent when that is wat they want, and providing a sympathetic and understanding ear when they feel they need to talk, about the person they hav lost, or anything else. Listening is often a greater gift than speaking.