I had an interview with the hiring manager, it went well, two days later he called me and told me how much they would pay me and when my start date was. He also said I would be receiving an offer letter via e-mail. It has been a week, the date that we agreed I would start is fast approaching, and still no e-mail.

I sent a follow up e-mail this morning, haven't heard anything back yet. Should I be worried that this is going to fall through? Do I just show up on the date that we agreed to? This will be my first job out of college and the anticipation and anxiety are killing me.