Small claims court is your only hope.

If the utilities are in your name, YOU are rersponsible for usage on that account.

you really needed to deal with this a month ago...

never expect a roomate to pay up once you're out....of course, sometimes, that $300 is worth it to make sure you never ever see them again...

had to do that once, dude wouldn't transfer the utilities into his name after i moved out- so I turned it all off on him at the end of the billing cycle.

I'd rather live with roaches than mammalian parasites ;)

Bicycle -- was your name on the rental agreement/lease for the apartment? If so, the landlord should have given your half of the deposit back to you, not to your roommate. If the rental agreement/lease was in your roommate's name, the burden of proof would be on you to prove that you and roomie agreed that half of the deposit would be refunded to you. As LazyGardens said, since the electricity was in your name, you are legally responsible for the bill, absent an agreement to the contrary -- an agreement that, again, you'd have to prove. Basically, depending on your state's laws, an oral agreement is binding, if you can prove that there was an oral agreement. So, it's always much "safer" to get all agreements in writing. Whether the roommate situation is purely platonic or as lovers, ALWAYS, ALWAYS, ALWAYS get agreements like this IN WRITING at the BEGINNING of the living-together arrangement. Saves so many problems at the other end...

I find myself wondering, though, how your roommate "ran up a $350 electric bill." I'm guessing that it was a failure to pay for one or more months, and that you didn't realize this. As soon as you moved out, you should have had all utilities turned off that were under your name. If roomie still wanted electricity, he would have gotten service very quickly in his name, and he would have been paying for it.

You may have to write off the $350 as the cost of a Life Lesson. Making mistakes is OK. Repeating the mistake is not.

bIcyclelove..step one,,the electric is in your name so call the electric company and cancel the service.
Step two, file a small claims action, it doesnt cost much and in the end looser pays court costs too.
You will certainly be able to recover the outstanding electric bill but may not be able to recover the deposit since you left voluntarily before the lease expired.