What matters is the chipset.
The following are supported under Trisquel: 8187, 8187B, and 8187L, and
AR9170.
I'd reccomend the first three. The last one won't work on some free
distributions out of the box. They could/should if the distribution
maintainer makes a point to include the free firmware though. The other three
don't require firmware and are in the mainline and libre kernels. As a result
they work out of the box.
I'd recommend our adapter:
Penguin Wireless G USB Adapter for GNU / Linux
http://libre.thinkpenguin.com
USB adapters don't all contain the same chipset so an adapter that came with
the 8187B yesterday might ship with a different chipset today. This is
frequently the case even where the box/seller/manufacturer advertise the
chipset (sadly).
