ATMs are strung out along Rte 13 in the tourist zone, including an ANZ machine outside Lankham Hotel. The Lankham also has a useful currency exchange counter that offers decent rates and does cash advances on Visa cards for a small commission.
BCEL Bank with a dedicated English-speaking counter that changes dollar- and euro-denominated travellers cheques (1% commission) and gives cash advances on Visa and MasterCard (3%). Its exchange office next door has longer hours, and you'll find BCEL ATMs around the city.
Lao Development Bank Changes cash and travellers cheques. Also houses a Western Union (money transfers only available weekdays).