What can one do about too much dust?

This is a serious question. The amount of dust in my house is about to drive me crazy. For some reason it seems worse lately (read summer) than it was in the winter. Here are the facts:

I have two large dogs.
I change my furnace filters regularly.
I sweep and dust to no avail.
My windows are closed and the AC is on.

Does getting one’s ducts sucked really help with dust or is this another fraud perpetrated on consumers?

What else can one do?