I liked Rollyo, and created a little roll that allows me to search Instructables and WikiHow for how-to kinds of things. I have to say, though, that I'm not that enthused. I think I prefer to search more directly on my own.
What I'd really like is a way to create a custom Google search using some of their sooper sekrit tags. My favorite is allintext:, which looks for your search terms only in the body of the page, ignoring titles, headers, footers, etc. It's surprising how much more targeted my results get with that in my search.
For more on digging into Google's guts, read the first few chapters of the book Mining Google Web Services. Great stuff!