On the blog lately, someone mentioned not knowing how to help a depressed person. These ideas will not work for everyone, and are far from complete, but it's a sample of things that have helped me. Perhaps you have more and you can list them in the comments section or even put together a short list of your own in the form of a blog...
Deliver cooked food that just needs warming. This is a biggie. I don't know of anyone who doesn't find this helpful, depressed or not.
Visit, read the signs that imply your company is wanted... if you're offered a cup of tea, stay for tea. If you're not offered, ask if you can make one for them. If the answer is "No thank you", retreat and allow space. But do not stop visiting. Just make your visits regular, but very short. This builds trust.
Drop a text. Every day or every other day. It tells them they are being thought of and that they matter.
If face to face discussions are difficult, find another way to communicate. There are countless ways.
Be honest and say what you're thinking. Say that you want to help but that you need to be told how to help. One of the best things I have ever seen about helping someone with depression was a cartoon strip. It shows a depressed person being asked questions:
What is wrong with you?
I don't know.
How can I help?
I don't know.
(builds a nest from cushions)
Come in here, I built a nest and I'll stay with you until you feel better.
That is what we really need to hear.
The room above the garage.