Same day Paraguay Visa

(Note that British and South African (and I believe most European) passport holders do not need a visa to enter Paraguay)

The Paraguay Consulate in Posadas, Argentina is in a small, orange, old colonial house a couple of blocks from the town center at 179 San Lorenzo (the street numbers were changed but the locals still prefer the old numbers - the new number is on the 1500 block) between Santa Fe and Sarmiento. There is no sign on the building, just a Paraguayan flag (red, white, and blue broad stripes) hanging in front with the old street address - 179. I entered the air-conditioned consulate on a Monday morning and there were just a few people inside and I didn´t wait more than a minute, not like the chaos at the consulate in Buenos Aires. The requirements for American citizens are to get 3 photocopies for each of the following:

1. Passport Info Page
2. Argentina Entry Stamp(in passport)
3. A credit card(only front side)
4. Round-trip transport (it appears you can´t just buy a bus ticket to Encarnación from Posadas - in the unlikely event they do require proof of onward travel you could book a tour to the Jesuit Ruins just 30k inside Paraguay from one of numerous travel agents in Posadas)

In addition to the above you need to give them 3 passport photos which you can get along with the photocopies at a shop right next door for US$4.
A single entry visa cost US$65 and a multiple entry visa costs US$100 in cash only and they provide change.
You then fill out a simple one page personal info form. (if you make a mistake and cross anything out like I did you will have to fill out a new form)
After about an hour he will ask for your right thumb print on three pages which you will also sign.
Even though there was a Yellow fever outbreak in Paraguay there were no requirements or even notification. I got a free yellow fever shot at the hospital two blocks from the bus station in Encarnación, after I crossed the river into Paraguay.
The whole process can take around 2 hours.

The frequent(every 10 minutes) and crowded local bus is clearly marked "Argentina - Paraguay" or "Servicio Internacional." It costs 11 AR$ and you can catch it on Entre Rios, just a couple blocks south of the town center.