If a guy wanted to give some money to a charity, which one would you recommend and why?
Medecins Sans Frontieres & Cancer Lifeline.
I donate the majority of my yearly charity contributions to MSF. They do excellent, absolutely necessary work across the world and use their funds wisely.
Cancer Lifeline is something my mother participates in. The best thing that they do is offer cancer patients the ability to call the lifeline and just talk. From talking to her, what happens is that most people who are diagnosed with cancer often receive significant support from family and friends initially but as time goes on and the disease has taken it's toll they are often left alone with no one to talk to. Patients will often call and talk about absolutely nothing for an hour or more and feel better.
We're so obsessed with treating cancer and finding cures (which is great) that we often forget the people who actually have it and have to deal with it on a daily basis.
I'm glad you've chosen to start (or continue) giving. I started giving when I was in college and had no money and I felt like it was absolutely worthwhile.