I have tried a few pen pal sites in the past, but Global Pen Friends is the best :) there are no annoying ads, and I really like to see what categories I have in common with the others!
I absolutely love using this site to make penpals and friends! I have met some amazing people here and have sent several letters. If you are hesitant on getting started, don't! I'll be using this for the rest of my life if it is around still too haha. 20/10