Someone else might have a better answer for this, but basically you can use a photo page as the album gateway page. Drag a photo you want to represent a particular album to the space where you want it, create individual pages for each album selected, then on the "gateway" page, drag the icon for each album page to the appropriate photo in order to create a link to that page. I hope that I'm explaining that clearly enough.
Example.
Say you have two albums, one is for apples, one is for oranges. On your "album gateway" you'll have a photo of an apple and a photo of an orange. Drag the iWeb page icons for the orange album to the orange photo and the one for the apple page to the apple photo in order to create the links. On the published site clicking the orange will take you to the orange gallery and the apple, to the apple gallery.
I think.