Mrs.TongToBe...I'm right there with you! I bought the invites, filled them out and just sent them yesterday. I'm a natural planner/organizer and I love doing it. My MOH is in the process of Moving and planning her sister's bridal shower that happens to be 2 weeks before mine. We're having it at my house because its the most centrally located for all the guests and has an awesome floor plan meant for parties :) The girls (BM's &MOH's) have it from here, but I can't help but want to be involved with decorating and such. Afterall, its kinda what I do for living.
Typically, the people responsible for planning and paying for the shower is the Bridal party and/or Mom, Grandma, etc.
I was a bridesmaid in a wedding and could see that no one else was stepping up so I threw it and asked the other bridesmaids to chip in- I planned another one for a friend because her MOH/sister lived out of town and the mother financed it all and gave me a very good budget so that one was easy! I always thought it was the MOH's duty