Check out Rabbi David Bar-Hayim's audio shi'urim on Sephirath HaOmer and on Lag b'Omer by clicking here, or download them directly by clicking on the links below.
Sephirath Ha Omer: The Bar Kokhba connection
The Misswah of Sefirath HaOmer: If You Skip a Day, Do You Make a Bracha?
Sephirath HaOmer: How Did the Talmidhim of Rabbi Aqiva Die?
Lag B’Omer: A Holiday With No Reason
Rabbi David Bar-Hayim, Rosh Machon Shilo, can contacted at email@example.com.