Several people have posted on the atheist bus slogan generator which is good fun to play around with.  For some of the best ones I've seen follow the links here here here and here

For what it's worth, and it's not remotely funny, here's one I generated this afternoon when I got back from lunch club.  We load up to 50 wrinklies onto a coach and bundle a few more into cars and have lots of fun - even if I do sometimes wonder why it took me four years of theology to train to do it.  The first line is a kind of slogan I've used for our church a fair bit in the last five years, the second reflects lunch club life.

On a journey with God

Climb aboard and join the fun