I'm sure this has been covered before, but thought I would give a quick update on getting a 60 tourist visa in Vientiane. Handed in on Monday, which I think is the busiest day. Arrived at 8:30 and handed in the documents at 9:30 (Application form with 2 passport photos and copies of my inside passport page, Lao visa and entry stamp). I received around number 270. My number was called up the next day at around 2:30pm to give an estimate of how quickly they get through them.
If you are flying back from Udon Thani, I found that one cheap way to do it is take the bus from the central station next to the market (22'000 kip). It drops you off at the bus station next to central department. They also have metred taxis outside Central which cost me around 70 baht to the airport. I'm not sure if that is any cheaper than tuk tuks.