Leaving a job w/o burning a bridge

[ttleistdci]

I've been at my current job with a small startup company for a few years now, and just accepted a job offer that will pay me a decent amount more plus will give me some benefits I didn't have before.

I plan on letting my boss know today that I'm leaving. I told the new place I could not start until June 20th to give my boss ample time to fill my position. This was totally out of respect for him as I could have easily given 2 weeks today and started the new job the beginning of June.

I'm going to let him know that I can still help him out on the side with graphics, ads, etc. (things I can do from home in my spare time for some extra cash).

Any suggestions on how I let him know? It may sound like a dumb question, but I've never been a real job whore so I don't have tons of experience in giving notice and stuff. I'd like to do this in a way that he won't take it personal and I can continue some type of business relationship with the company.