Visas & Visa extensions
Prices range from US$30 to US$42 depending on nationality - Australians pay $30, Canadians US$42, Chileans US$30, Belgians US$30, British, Dutch US$35, Swedes US$31.
Visas can be obtained in advance from Lao embassies/consulates. The fee varies by nationality/embassy; US$20 is common. Processing times also vary; 2-3 days is typical, though you may be able to pay an extra small amount to receive the visa in as little as one hour. InPhnom Penh the travel agencies can arrange the visa the same day (but may charge as much as US$58) while getting it from the embassy takes a few days. Getting a visa from the embassy in Bangkok costs around 1400B for most nationalities, plus 200B more for "same day" processing. It's cheaper and quicker to get one at the border.
There are Visa-on-Arrival facilities at the international airports in Vientiane, Luang Prabang and Pakse, and at all border crossings with the exception when entering overland from Cambodia. The cost varies between US$30 and $42 (if paid with US$ notes; paying with Thai baht will cost considerably more and border officials will not accept Lao kip at all). A US$1 "out of office hours" surcharge, and a small (possibly 10 baht) entry stamp fee, might also be charged.
Entry permit extensions (sometimes referred to as "visa extensions") are available from the Immigration Department in Vientiane (US$2 per day) and via agencies elsewhere in Laos (who will courier your passport to Vientiane and back again, around US$3 per day minimum of 7 days).