Hi Avrile, I am happy to know that you're beginning to appreciate countertenors. Here are some of the famous countertenors of today. First is Derek Lee Ragin, an American countertenor. Aside from being a master in vocal style, he also interprets contemporary music. His recent performance was March 22, 2007. Second is Hurley David, an English countertenor. He is the lead countertenor of the well known international group King's Singers. Third is Michael Chance, an English countertenor. He performed last year a Bangkok opera "Ayodhya". Last is Yuri Borisov, a Russian countertenor. He performed last August 2005 to one of world's famous festival the Edinburg Fringe. It is a series of eleven concerts of Russian art andf folk songs.
I agree to you that most countertenors sang repertoires from Baroque and Renaissance periods. They always sing arias and cantatas from the works of Handel, Purcell, Vivaldi and Scarlatti and many more. This is because during the Baroque period there is an increase of popularity of opera. Many operas were written with roles for castrati and countertenors were the one's who replace them.
I hope my answers to your questions made you more interested in listening to countertenors.