the monthly database quotas here are, in my opinion, sort of a joke. IF you are surpoassing the limit then I can say without reservation that you have a site that's busy enough to profit from. That's profit, as in, after it pays for your hosting bill each month
and heck yeah, Google's a great simple alternative, I'm actually putting web/image/groups/news searches on my personal site redesign since I use both my personal site and Google everyday for the most part.
This will allow users to enter a query on your site OR the web depending on how they enter into the text box:
And this will do your site (transparently) only:
much quicker and easier than an application you have to upload, configure, hack on etc. Keep in mind that you're at the mercy of the Googlebot and their cache as to what gets returned however.