Why are you interested in Korean?

재미있다/재밌다 means something is fun or amusing. "To be interested in something" is usually expressed as -에 관심이 있다/많다, -에 흥미를 느낀다, etc.

Also, what is a "fun" way to say "member" in Korean. Google Translate shows: "회원", but I wonder if there's a way to say "member" in Korean that is a little more interesting and fun than that?

I can't think of a fun way of saying "member".  To make it sound  more important, you might say 창립 멤버/회원 (founding member), although it's a big word for such a small thing.  Or you could say something like 일찍 가입하셔서 선수가 되어 보세요 (Join early and become a pro), where 선수 normally means an (official) athelete but also has the slangy sense of someone who is very good at something, like a pro.

Thanks!
Dave