Dan,
PhotoSmash supports multiple galleries per page. The trick is that you have to supply the gallery IDs if you're doing more than one in a post or a page...like:
[photosmash id=5]
[photosmash id=8]
That would show galleries 5 and 8 right after each other.
I don't think that Excerpts do shortcodes, but hopefully you can just use the regular post/page to get your multiple galleries.
One thing that is coming to PhotoSmash Extend is to allow creating Gallery Viewer pages, which would give an index of your galleries, and clicking a gallery would show the selected gallery...but that's a bit down the road.
Hope that helps,
Byron