In PhotoShop Versions 5 & 6, to have a flattened layer above your individual layers you do the following:

1. Create a new layer above all your other layers.
2. Hold down the Alt key.
3. Go to Layers, Merge Visible

Now your have a flattened version plus all your individual layers.

Control + E merges down.

I did not know that. Very useful tip - thanks.

Thanks Sharon,
Now alot more members will be able to find this excellent tip whether they are looking for it or not.
DJ