Efunda, I have an idea for you guys.
My coupla pennies:
The way registration for an engineer works in the U.S. is that the engineer is ultimately responsible for anything he or she does. A book-smart mathematician with good surfing skills can get on the net and get enough information to produce drawings on a piece of high-speed rotating machinery or a 50 story building. If he could get the funding he could build either one. If something goes wrong, he's responsible ALONG with the folks that listened to him and built it.
In an engineer's case, if something goes wrong it is the engineer who is LEGALLY liable. The folks that built it (if done properly) are off the hook.
What you have proposed is a toolbox. Anyone can use it, and they do it at their own peril. As most of the other posts have said, there is much more to engineering than math and formulas - but math and formulas are all you can realistically put on a site like this and that is OK. What about all the formulas that are already on this site? Can't they be misused by non-technical folks leading to injury? Is the site or anyone that posted those formulas to blame? The answer is no, and courts have upheld that view.
In conclusion, I don't see a problem with having an area with Excel spreadsheets and the like posted for solving different specific problems. It is up to the engineer to implement the tool correctly and check the results...
Side note - in regards to checking, it is my opinion an engineer should know the answer before the calculation is done. It should be immediately obvious if a program or tool isn't giving the right answers. This is another reason the toolbox is OK - the mathematician won't know if his answer is correct...