I have a good idea for a new project - How much should I tell a web and application developer about it?

Tell it someone, who you trust :)

It is a ***** seeing someone else get the glory and fortunes of our ideas, had it happen too often.

Learn about protection of intellectual property as you are doing now. There are boilerplate forms for the printing of Non-Disclosure forms which is given to the person you show your idea to for their signature before revealing the idea. There are a few lawyers that specialize in protection of intellectual properties and it might be worth your while to have at least an introductory conversation with one or two. I would also check out the govt printing office as they may have pamphets on this already. A local Bar Association will be able to help you find the lawyers you seek.

It might be helpful to have your idea printed out and taken to be notarized first of all.

If it is your intention to pursue the idea as a commercial venture let those you speak to about it know that is your intention otherwise there is room for them to steal it on the premise that they were sure you were just talking aboutand would not do anything about it. Keep a record of to whom you show it, when, where and a summary of the meeting. If a company gives you an agreement to sign, read it well or best have it read by someone who knows what that "undotted i" really means. Good luck. Hearing "you can trust me" usually means you can;t