Since I have entered and left Laos 3 times I'll share my experiences here.
Visas: for most people available at the border, but not all borders. 25$ or equivalent in Thai Baht for 30 days.
Bike docu: usually none. Don't volunteer the info that you have a bike and save time and money. If you do get a "Laisser Passer" it takes quite some time to issue, I forgot how much it costs, but it's only valid for about a week or two, so if you stay longer you will have to find a customs office for an extension. Leaving without one is no problem.
Insurance: probably a good idea to have, otherwise you could find yourself in jail after an accident. May not be available at smaller crossings. Look for a blue and while "AGL" sign to find an insurance office.
Map here: Thailand - Laos - Cambodia - Myanmar Border Crossings: Motorcycle Touring
Huay Xai/Chiang Khong: ferry crossing, 500 B/bike. Don't try this in the afternoon, as the ferries only run for trucks. U can get stranded, stamped out of the country and no ferry going. The Mekong Boat Mafia will then attempt to get you to lift your bike into a small boat, for an additional charge.
Nam Ngeun/Huai Khon: supposedly opened for intl. travel Dec. 2008. VOA unknown. Lots of fun dirt roads leading to Luang Prabang. No go in the wet. Highway 2W to the North is being sealed.
Nam Heung/Tha Li: Fully open now and VOA. Road East to VT under construction. The long road North to Luang Prabang is very big, busy and dusty.
Friendship Bridge 1 VT/Nong Khai: no entry to Laos for bikes, but exit OK.
Muang Paxsan/Bung Khan: ferry crossing, fairly busy, weekdays only. No VOA. Visas available at the consulate in Khon Kaen, Mo-Fr 9-16h,
171 Prachasamosorn rd, N16 26.164 E102 50.999
Thakek/Nakhon Phanom: ferry crossing, weekdays only, VOA.
Friendship Bridge 2 Savannakhet/Mukdahan: CLOSED TO BIKES! In fact, closed to anything with less than 4 wheels. However, if you go and see the head of immigration and talk to him nicely he may arrange for you to leave on your bike. You CAN take your bike in or out on the back of a pickup, etc.
Vang Tau/Chong Mek: Land border crossing, easy, VOA. However, no entry to Thai registered bikes under 150cc. Exit OK for all.
Donglor to Cambodia: entering Laos no problem, although no VOA. To enter Cambodia with a vehicle customs now demand a permit from Phnom Penh. Some people have been turned back, we were asked for a bribe of 20$ each bike.
China and Vietnam are effectively closed to vehicles, so I'm not covering the crossings here.
For up-to-date info search the forum at The Golden Triangle Rider :: Laos - Any message