The numbers I have, coming from an analysis I did of a [small?] corpus of light novels [150 volumes, 20 authors, half a million sentences, proper stemming], are these:

わかる: 14178 hits (69.27%)
分かる: 4240 hits (20.72%)
分る: 93 hits (0.45%)
判る: 733 hits (3.58%)
解る: 1224 hits (5.98%)

Frankly, I don't care about which is more common anymore.
I posted originally as an afterthought because, heck, I've seen googlefights before.

What I find weird is how people can search for the same things and get conflicting results. I'm not expecting them to be exactly the same, but if it changes a lot, which I find interesting. Case in point: 分かる with no quotes. I got 34 million, you got 252 million. That's over 7 times the amount I got.
I'm not sure what it is, but simple calculation errors just don't seem like it could make up for 218 million results.

Yeah. Tru dat.

It's interesting. I'm with the other guy who said that you just don't see it in hiragana much. I would guess that it's more common in blogs. I can say though, that in Japan I do not see it just in hiragana much. I can't remember the last time I saw it that way.

I will say though that in everyday use I think the other two characters are _underused_, as people are lazy about choosing the right one. Writing would be clearer if people used the other characters more ...

I usually use 分かる only, by the way.