I'd like to let people type math (latex) in a text field and show them the math content dynamically as they type on the same page. how can this be done (i'm developing on windows)? thanx!

For the dynamic updating part I suggest markitup. In preview mode it updates a "processed" version of what you type (just like the SO text fields). For the math, I also advise the excellent jsmath (checkout the examples!). A combination of the two should fit the bill.