Someone I know created a free e-course on how to succeed with men. I know it covers topics such as how to build self-esteem and initiate a conversation with other men. I believe it's still at whatmenseek.com
Aside from that, the technical term for the process of overcoming shyness is systematic desensitization. In other words, little by little you take steps in becoming more confident and at ease around other men.
First, for a few days you would visualize yourself approaching a guy you like, initiating a conversation with him, and then him responding well. After this, you would find opportunities to make small talk with different men you come across. For instance, when you go out grocery shopping, you would practice looking your cashier in the eye with a smile and asking him how his day is going.
Pretty much the more you talk to men and make small talk with them (whether they be your grocery store cashier, gas station cashier, car mechanic, etc.), the more at ease you'll become.