What are you building (residential, vehicle, hobby setup, etc)?
Larger residential/commercial panels have a better reputation for quality than a lot of the smaller panels sold on amazon (not that the smaller panels are bad panels by any means-- but its generally the larger panels you'll find with the 20-30 year warranties).
If you are building a stationary system without tight space constraints, worrying about panel efficiency isn't worthwhile. Cost and quality should be the primary determinants.
If cost is a big consideration checkout
santansolar.com, they have really good deals on new and somewhat used panels if you live in the West or SW US.
altestore.com is another good place to look.
As for brands, Sunpower, REC solar, Canadian Solar are all good brands, but there are probably at least a dozen other good brands. From the big I know, it seems that brand is less important with PV panels than with other components of your system so long as you get a somewhat reputable brand with a track record.
Good amount of info out their on residential and commercial panels, not so much info out there on the smaller panels.
This list might be a decent place to start (for residential panels)
edit: oops, missed the 100W stipulation in your title.