Good to hear, hope current events won't hamper your trip.
So let me get this straight - it seems there are 2 steps to get an Iranian visa.
1. Get a Letter of Invitation (LOI)
Best bet are travel agencies like amoot, key2persia, stantours, persianvoyages. For a fee they get you a LOI which then allows you to proceed to step #2:
2. Apply for a visa
Options for this appear to be:
The official Online Electronic Visa Service website http://evisa.mfa.gov.ir:7780/mfa/
IranianVisa.com (is this official or just a travel agency?)
The process can apparently take anywhere from 15 days to 2 months, getting denied is not unlikely (especially in current political climate after the elections) and the visa, when issued, is valid for 3 months and allows you to travel in Iran for 30 days. It is possible to extend it when you're in the country.
Makes sense, or am I confusing something? I'm about to embark on a visa-hunting expedition for Iran and Pakistan and am wondering what the best way to attack this is.