Long time lurker, first time posting.
Using quality material and tight joinery, building an entry door is not as daunting as one might expect. Honduran mahogany and white oak are my preference for exterior doors. Laminate stock for your thickness, don't rely on 8/4 & 12/4 material. I'll use quarter sawn material when I can get it. Quarter sawn mahogany is very cool looking.
A quality spar urathane or varnish is a must. My first choice is Waterlox, Zar exterior urathane is also very good. (Not their water base!)
I've gained a lot from lurking on htis forum and now it's my opportunity to give something back. Let me know what specific questions you have and I'll do my best to answer them.
Here is a link to some of the doors we have built, hope that's o.k.
scobiscompany/doors.htm
Regards,
Mike Rachocki