Searching through multiple search engine only in a single-click is nothing new. I've seen plenty of websites offering such service. Those websites, as far as I know, does not provide a search engine by itself. They basically relied on other search engines such as Google Search, Yahoo Search, MSN Search, or Live Search.
In my opinion, the idea was quite old that it might explain why there isn't so many of them popping out these days. I never really like using multiple search engines at once. I have to admit that I never got a full grasp of what these services are good for. Hence I always use a single dedicated search engine to handle my search keywords -yes, it's Google.
That being said, I have below some snapshots of websites offering multiple search. While I'm still not interested in using these services, others might find them very useful.
Putting six snapshots should be plenty of KBytes to download so I won't go any further. I'm sure there're more multiple search engine services like the ones I grab above. If you're really that curious then you know where to search.