how soon after breaking up can I start talking to other guys?

My boyfriend and I just broke up after 2 years together..about a week and a half ago..but I think it was a really long time coming and it was painful when we broke up but since then I haven't been feeling as terrible as I thought it would be at all. I mean, yes I cried a couple times, but it wasn't anything that tore me apart. We had a lot of drama and fights and mistrust towards me (that was completely unjustified by anything I have ever done) so we mutually decided to part. We also decided to stay friends and still go to class together (we drive to the University together so we pay less for parking). But since we broke up, my ex has taken down all our pictures, as well as writing some passive aggressive things on his facebook page (he liked a page that said "oh cool you're dating my ex. I'm eating a sandwich, would you like those leftovers as well?") and things of that sort, yet he still talks to me like we're friends (like he asked me how my weekend was).

He's acting like a total jerk online, being very public about being single again, and going out, which I have not done yet..then talks to me like it's okay and I'm not affected by it at all.

I feel like I have moved on from him a long time ago. I don't think we had much of a relationship for the past 6 months, if not more than that..so it's not as heartbreaking as I thought it would be.

so my question is, when can I start talking to other guys? I mean, I don't want my ex to go and bad mouth me to everyone since we have a lot of mutual friends (although most have sided with me cause they see how immature he is online..), but on the other hand, he's a big jerk and I don't want to have much to do with him right now..

what should I do? I'm just confused on how I should act..I don't want to stoop down to his level, because what he's done is pretty low, but on the other hand, I feel like it's because he's hurt, and I want to be friends in the future..

so..help? any ideas, advice, comments? please?