From the Even Gentiles Can Have Chutzpah Dept.:
(Seen yesterday at a Baptist church)
TITHE IF YOU LOVE JESUS
ANYONE CAN HONK
From the Dubious Analogy Dept.:
(Seen years ago at a Methodist church)
SMALLNESS NEVER KEPT A MOSQUITO FROM BEING EFFECTIVE
A readerboard is that sign by the road with big movable letters on it. The above are messages I have personally seen on church readerboards.
Just this weekend, my sister and I were having a rather flippant discussion about the more earthy aspects of a career in prostitution when we passed a readboard that read “Only Jesus can fill the emptiness inside”.
I giggled like a schoolgirl.
Jesus – all deity – but also all man! 
One I saw a long time ago said:
Satan Promotes Truth Decay
I pass a Quaker meeting hall everyday with such a readerboard. For much of the summer it read:
TORTURE IS WRONG
Well, okay. I’d like to think most people know this already, but, hey, it’s your readerboard. I think I’m missing something with the current message, though:
IF YOU ARE NOT HAPPY
HERE AND NOW THEN
YOU NEVER WILL BE
Not very comforting. And “JUST GIVE UP” would be easier to read while driving…
I think that might be an admonition against pinning one’s hopes for happiness on the idea of heaven, and not living your life to the full.
There is a Baptist church near here that generally has your typical religious messages on their board, along with the typical bad puns.
But a couple of years ago, when we had a bit of rain during an otherwise drought-plagued summer, the board read:
“Thanks for the rain. Now can You do something about the Cubs?”
“Laying at home on your back, screaming, “Oh, God!”, does not constitute prayer.”
Just kidding, I never actually saw that one.
There was one church in SC that must have had a third grader putting up the letters, because I cannot tell you how many misspelled words, poor grammar, and just wrong words they used.
The one I remember most was, “Eating unforbidden fruit can get you into a jam.”
Ummmm…
There’s a Methodist church down the road that usually has nice readerboard messages. They’re never really over-the-top, just decent.
I was giddy when I drove by a couple weeks ago and saw, under their message, “Go Tribe!”
But alas, it would seem that God doesn’t read readerboards 
We used to have a big blue-and-white sign up on our readerboard during the playoffs: “God doesn’t take sides… but we do! Go Leafs Go!”
Then some people, hopefully now with karma’s foot wedged firmly up their collective arses, stole it.
There’s a church in the town where I grew up that had the best messages ever. Unfortunately, I can only remember two at the moment:
TRY US OUT
OUR SUNDAYS ARE
BETTER THAN DAIRY QUEEN
and:
YOU CAN DO A LOT
OF GREAT THINGS
WHEN YOU’RE ON YOUR KNEES
One of my all-time favorites was in Tennessee:
TODAY: (some name) FUNERAL AND MEMORIAL SERVICE
TOMORROW: DUNKING BOOTH
I like the church signs that don’t really have much to do with religion:
“Friends are like fudge.
They’re sweet, with a few nuts.”
A few years ago, the church I grew up in (I left it long ago, but my parents were still there when this happened) put the following text on its readerboard:
PROUDLY SERVING STARBUCKS
We were speechless. What they meant was that the coffee at the after-church receptions was being provided by Starbucks. But what happened to “thou shalt have no other gods before me?”
Yes, they took the sign down, but not because of public or even congregational outcry. For copyright reasons, Starbucks made them take it down.