Missing London Marathon because of an injury

Hi,
I've had to pull out of the London Marathon at the very last minute because of an injury. I'm totally gutted, as I had to make the decision yesterday (Friday 15th). To cut a long story short I crunched my back as I was tapering last week. It was going to be my 4th marathon, and it was probably the right decision. Anyway, I now want to focus on another marathon and wandered if anybody had any suggestions or advice on what to target. I've had a look at up and coming events over the next couple of months, and there are a few out there – be a shame to waste my fitness, now Im in good shape (minus the injury).
Any suggestions greatly received.
Thanks in advance
Tom