Fortunately, I work at the school where we attend church and my 2 1/2 year old son has always been pretty good when we attend since he knows so many people there. However, it was very rough keeping him occupied when he was just starting to toddle.
One thing that helped us out was sitting in the very front (we're actually in row three). He can see what's happening and that helps a ton. We have a set seat with the same people behind us each week - also with small kids (pre-schoolers who love to play with my son). This way when he drops things or starts to play continuous games of "peek-a-boo," it's not too distracting.
Now that he's older, he tries to participate (putting the money in the collection basket) and if nothing else, he makes sure the priest and other ministers/lectors/altar servers get a high five both on the way in and out of church.
I also agree with the poster who mentioned family services. Our priest loves to have the kids up close and personal - our 10am mass is considered FAMILY mass.
Good luck!