For the bedding available in the U.S.:
Aspen bedding is the safest and highest recommended in terms of wood shavings. Different brands have different style shavings, so I'd look for the softest finer shredded variety. I found Petco cedar to be a bit harsh, but there are some other brands that shave their finer and softer. Pine is not safe for hamsters or cedar and should not be used.
Carefresh is quite good, and you can get a pretty good deal on 60 liter bags at Petco.com (~$14 per bag of Natural if you buy on-line). It's soft, hypoallergenic, and is great for tunnel-making. Natural has a bit of a cardboard smell.
http://www.petco.com/product/3370/Ca...20Bedding-3370
I've used EcoBedding and it's fairly good. Doesn't smell at all, looks pretty, hypoallergenic and neat. Fluffs up pretty well once out of the bag, so you need much less than you think per cage refill. Can find it for a good deal on line for the largest bag.
http://www.amazon.com/FiberCore-Smal...7860130&sr=8-2
I've read Sun Seed Fresh World bedding is good. It's sort of between Carefresh and denser pelleted paper bedding.
http://www.petsmart.com/product/inde...397136.4397207