Google Answers was a great service I used and recommended. Sadly it was closed. Many of the free-lance researches from Google Answers moved to a new independently owned site, Uclue, that offers a similar service. You ask a question, announce a price you think an answer is worth, and if a top-notch researcher thinks your fee is fair, they will research your question. Questions can be quickies worth $5, or more complicated queries costing $200.
In my experience their answers are solid and reliable. You can always ask for clarifications. As with Google Answers, the results are public. That means it pays to search the site for previous similar questions. It also means that your answer won’t be confidential. (Indeed. The answer to a question I commissioned on Uclue was Slashdotted.)
If you want advice, go to the free and free-wheeling Yahoo Answers. You’ll get your money’s worth. If you want help on a particular question that the exact right person can answer quickly, I think Ask Metafilter is by far the best guru (and it is free for members). But if what you need is some real research and serious sleuthing, the kind of answer that is not just sitting in someone’s head, I believe your best bet will be Uclue.
Figure how long it might take you to answer your own question — if you could at all — and you’ll see that Uclue answers are a real bargain.