If I had to choose one person as the most influential for promoting the joy of math, it will have to be Richard Rusczyk. I still remember fondly calling him the "funny guy" when I watched his "Commutative Property of Addition" video at six. He opened a door into the fantastic world of math for me, as he did for many many other kids.  If you are just getting started, create an account on AOPS NOW -- as all self-respecting mathletes do -- and start the fun. Practice using Alcumus, seek thrill at For The Win, or just chill at the forums, where many of your peers hang out. 

Dr. Titu Andreescu, former head coach of the USA IMO team, founder of the Awesome Math Camp,  and author of the awesome Awesome Math book series, created the purple comet math competition. The questions are smartly designed and a lot of fun to tackle. If you have a group of math friends, try form a team and participate! If you ever run out of AMC 10 / 12 problems (or even easy to medium AIME problems) to practice, Purple Comet problems are a good fit.

At one point (around JMO/AMO), you might be stuck and looking for resources that go beyond the intro level stuff covered by above web sites. Enter Evan, the OP bro who wrote what I believe is still the best book on advanced level geometry (EGMO book), not to mention the Otis course.  But it doesn't stop at math. Evan's wisdom shared through his blogs, Power Overwhelming, will certainly inspire, enlighten, and motivate you on your math journey. (his blog on teaching, Stop Paying Me Per Hour, help tremendously in shaping my pedagogy)

• • The Are of Craft of Problem Solving by Paul Reitz