I am a Canadian, travelling by bicycle. I wanted to quickly share my experience regarding my application for an Iranian visa. Perhaps it will help you in your travels.
1) I read on LP that the hassle of the visa process is greatly reduced if you seek the help of an Iranian tour company. This is TRUE. I contacted www.uppersia.com, and after completing an application form and sending an e-copy of my passport, I had to wait only two weeks for a visa authorization number. The number comes from the Iranian Foreign Ministry and, as far as I know, you MUST have one to secure a visa. I had to pay them $35, but honestly, I think it was worth it. The staff were extremely patient and professional - I sent tons of e-mails with questions and each was answered promptly, usually within the hour.
2) With my authorization number I went to the Iranian consulate in Trabzon, Turkey, the location I'd indicated on my application form. I picked it because many people have said that getting a vsia in Trabzon is a breeze. At least for Canadians, this is absolutely FALSE. Don't even waste your time. The consulate director took one look at my passport and immediately his attitude went cold. He pretended not to know what my authorization code was for, then said it "meant nothing." Finally, he said that a visa to Iran was "quite impossible." I asked why and he said, "because you're Canadian." End of discussion. The door was slammed behind me.
3) My only option was to try again somewhere else, so I contacted them and asked that they resend my application to the Iranian FM and have a new authorization code forwarded to the embassy in Tbilisi, Georgia. It was no problem whatsoever and I didn't have to pay extra money for the additional work. Within one week I received my new number, just as I was promised.
4) The staff at the Iranian embassy in Tbilisi were not friendly, but I was very polite and, more importantly, persistent. After arriving, I was told to come back in three hours. So I did. At that point I filled out an application form, surrendered my passport, submitted a photocopy of it along with two photos and paid 60 Euros. Then I was told to come back the next afternoon at 3:00. The next day, at 3:00, I was told to come back in 90 minutes. I think it's mostly a ploy to weed out people who kinda-sorta want to visit Iran. I REALLY want to go, so I kept showing up with a smile. It paid off. A half hour before the office closed I was given my 30-day visa.
My experience might have been a fluke - I can't say for sure. Either way, I just wanted to say that it is POSSIBLE to get an Iranian visa in Tbilisi. Even for evil Canadians.
Answer: For Iran visa just fill in the visa form on http://www.uppersia.com/Iran-travel-services/iran-visa.html, it takes about 10 working days to get your reference number and two working days to collect your visa at the embassy by direct referral or one working week by posting the docs to the embassy. You can pay the visa fee in cash in Iran.
Check the cheapest Iran tours at http://www.uppersia.com/Iran-tours