I have a Washburn D10SCE acoustic-electric guitar, and I noticed today that it looks like the bridge is pulling away from the soundboard! While tuned, it is very noticeable and I can see the wood splinters underneath the bridge (or maybe that's the glue...).

I have detuned it to prevent(?) it from pulling up anymore, and it has gone down a little. It is still wide enough to fit a pick in between the bridge and soundboard. If this is a major issue, and I think it is, what is it going to take to get this fixed? And should I leave it detuned until I can get it looked at?

id imagine i would be a major issue, i'd leave the strings slack til you get it fixed, maybe phone your local guitar repairer or music instrument shop and ask them what they could reccomend. how long have you had the guitar? where did you buy it?
Belief is a beautiful armour but makes for the heaviest sword.
This is a relatively common problem. The guitar needs the bridge taken off and then glued on again. It's easy to do but you need special clamps in order to put the pressure in the right places so unless you are a woodworker with the right clamps it's cheapest to take it to a luthier and have them fix it for you.
Thanks for the quick responses guys! I've had the guitar about 2 years and I don't know where it was bought because it was a Christmas gift.

Any ideas on the general range a repair like what CorduroyEW is talking about would cost?
Prices to fix an instrument very greatly depending on where you live. The only way to know what it's going to cost in your area is to call up some local luthiers and/or music shops that do repair work.