Here is a slightly useful page, it contains links to 'Multiple Search Interfaces'. If you want to know more about these Click here !

Anyway here are a couple I'll be adding more as time goes on, well I hope to anyway - time permitting.

The ALL4ONE Search MachineIt can access to four search engines
4 Metacrawler accesses 10 search engines
Motherloadaccesses 9 search engines
SavvySearchaccesses 23 search engines
CUSI This one gets a special mention because it's not only a multiple search engine interface but has a whole host of other search features e.g People etc

This page is incomplete and I will be adding more links as time goes on. (He promises !)