It's most probably the busiest place in town and good place to buy nice sticky rice baskets in variety of patterns - these are appreciated by local Sayaboulis. There are few stalls with gold and jewlery - I got some cheap and old bank notes and Indochina coins there (much cheaper than in Vientiane at the Morning Market). Try some of delicious, locally grown fruits and vegetables - especially bananas, mangosteens, pineapple, banana flowers and variety of fish from the river: it's fresh and tasty.
In the noodle shops near the market there are good places to drink ice cold Lao coffe and eat noodle soup - best to visit before noon.
This is trully the best place to eat in Sayabouly town (or more precisely - at the outskirts of town), especially for fresh fish from Nam Tien reservoir. They have large menu and use good, fresh ingredients for mostly local - Lao and Thai dishes and for good price: we paid about 45 000 KIP for one kg of fish with applied sauce - it was delicious. Since Elephant festival their menu is also in English, although staff can speak very little of English themselves.
The restaurant is about 3 km from city centre. You'll need to follow the main road towards southern pick up station (by the road for Pak Lay) and turn into hills by the sign for the Nam Tien restaurant - about 2 km from the main road will get you into quiet surrounding above the lake with some nice views throughout the landscape. If weather is fine you'll see lush green rice fields and Elephant mountain behind.
On the second photo you can see the view of the lake. Sometimes there will be fishrmen with small boats.
There is one bus to Vientiane per day from the bus terminal North of town. You'll enter Road 13 in Luang Prabang province. From the same bus station you can travel to Luang Prabang (a few times a day by songthaew or local bus) and Hongsa (few times a week by pick up car, but not often in the wet season). Note that songthaews to LPB gets full easily and that it takes roughly about 4 hrs to reach LPB southern bus station. You'll cross Mekong by ferry once at Thadeua and until you reach Rd. 13 you'll drive up and down the hills on the unpaved road. It takes some time to figure the departure time for each songthaew because they don't leave on schedule so get ready for waiting or leaving sooner than you thought.
There is small pick up/songthaew station few km south of Xayabouly centre with daily connection to southern districts by the main road. At least one songthaew/pick up per day will be leaving to Pak Lay, usually around 1 pm - it depends when it gets full enough. Be ready for long waiting. If you're first customer you may sit next to the drivier but put something on the seat so that it is clear to other people that someone already took the seat - you don't have to wait inside (and I guess you won't since it gets too hot in few seconds). It takes more than 4 hrs to get to Pak Lay, price about 45000 KIP. If you're sitting outside you may need something to cover your eyes, hair, mouth and nose because you'll get dusty as soon as car starts driving. Wearing comfortable long sleeve cotton shirt is good in order to protect your skin from getting sunburned.