If you're looking for a general
IDE, I would recommend the Sun One Studio, Mobile Edition.
Some have said it's a hard find on the Sun site, but I had no problems download a copy. I think you have to be an early access member. Here's the product page for the
Sun One Studio, Mobile Edition Zucotto had an IDE, WhiteBoard SDK, but their site seems to lead to a 404 error page. Calls to their offices in both Canada and the US have led to non-answered phones, and all emails sent to the company have bounced back (with the exception of their info_at_zucotto_dot_com address, which has yet to be replied - apx. 1 month).
You could always stick with a non-IDE product (notepad, etc.), although I wouldn't recommend it. Even though an IDE may take away from your "learning" experience, my experience has proven that using an IDE can not only improve your coding, but will also help you in developing applications at a more rapid rate.
I remember reading somewhere that you could integrate the WTK (Wireless Toolkit) with many IDEs, including the Sun One Studio, Community Edition (free download) and
NetBeans IDE.
Hope that helps!