As-salaamu `alaykum
To the initial poster, it depends on what you need. A lot of people listen to Dr. Zakir Naik, Khalid Yasin and Ahmad Deedat (rahimahullaah), but they are not scholars of the Islamic sciences, rather their speciality is comparative religion, so they can teach you about Islaam in comparison to Christianity, and their main objective is to give da`wah to non-Muslims. For this purpose, and may Allaah reward them, I would encourage you to listen to students of knowledge and other lecturers, who can teach about hadeeth, fiqh and `aqeedah, since we all need some elementary knowledge in these matters. I would recommend Abu Uwais `Abdullaah `Alee, rahimahullaah. He was a very knowledgeable and charismatic teacher/lecturer. Some of his lectures and lessons can be found at the following link,
http://calltoislam.com/index.php?option=com_content&task=category§ionid=4&id=138&Itemid=26