I too used to be plagued by wishy-washy friends, and since waiting on finalization of plans can be a real pain, I decided to find some ways to deal with them.

The first thing I did was set up a google group for my friends. There are about 20 memebers in it and we share stuff between each other by email occasionally but also make plans.

The second thing I learned was never to entice people or make plans, but simply to announce plans. I'd email the group:

"I'm going hiking at Franconia Notch this weekend if anyone is interested. Leaving from my house around 10AM Saturday."

That's it. No waiting for replys, no waiting on people at all. If you want to come with me you'll be around at 10AM Saturday or you won't.

There's no frustration if its only me going, as I intended to go alone, and if anyone wants to come along then that's a pleasant surprise. But I won't base my activity schedule around waiting for them.

Surprisingly, since I started doing this, more people seem to come along. Motivation is contagious, I think, and it seems the thought of someone else already 100% committed to doing something makes it easier in the minds of others to commit themselves.

So make it easy for your friends. This way they don't feel guilty or obligated one way or the other, which is a huge relief for some personality types.

Later, I made a second google group for announcing house dinners, and now regularly 5-15 people show up every wednesday and we cook and eat together.