Iceland?
 

Any recs for Iceland? I've read that there is a ~$25 package from Siminn that gets a chunk of voice, text and data, which sounds decent...

Yes. There is.
SÃ*minn is the best network. 3G coverage even in areas where nobody seems to be alive. Vodafone is close behind. Both are good if you want to go the ring road.
Nova is the 3rd network. Much cheaper, but only good if you stay in the Reykjavik metro area.

Here is a survey of starter packs and data options. To call to the US, you can choose any VoIP provider.

http://prepaid-data-sim-card.wikia.com/wiki/Iceland

Sensorly.com has some coverage data for Iceland.

Thanks for the input... I also understand that both Siminn and Vodaphone offer data-only SIMs and corresponding plans, but that these can be hard to find retail (few stores carry them)...

Is there an easy outlet for such data-only SIMs in Reykjavik?

Well, I think a SIM is a SIM. It's the plan that regulates the data vs voice issue. I don't read Icelandic very well but it seems at least one shop at the Keflavik airport sells Siminn SIMS. They have a prepaid called "Frelsi" (Freedom) Within that there's a plan called "Sveigjanlegir" (Flexible) at three levels. Good @990 kr has up to 500 MB, Better @1990 kr has up to 1 GB and Best @ 3990 has up to 10 GB (1000 kr = $7.42)

The details are here: https://www.siminn.is/thjonusta/simi...i-bodi/frelsi/

What you need is a Net Frelsi sim from Siminn. Please keep in mind that:
1. Activation of data packages is done online, after loging in to their automatic account management service,
2. Account recharge seems to be also done online, using a credit card.
3. If you want to make use of the 3G (UMTS) high speed data services outside of main towns your device has to support UMTS 900MHz. That's the band used for 3G coverage in the so-called 'interior' and along unpopulated areas of the ring road.