A Usenet abbreviation, still sometimes seen on for-sale boards such as Carnegie Mellon University's popular cmu.misc.market bboard. Usually used in a subject line, but not always referring to a product or service that the user wants to buy (see also WTB). Examples of such subject lines include:
Note: the first two lines could involve the poster either buying or selling the item/service in question.
A recent thread on said bboard has suggested a few expansions for WTD: WanTeD, Want to Discuss, and Want to Deal. The third such example is generally accepted, but most users simply read it as "WTD."