Phone and Data Roaming Options
The Netherlands (NL)
Phone (& Data)
The best option in The Netherlands is probably to get a prepaid Vodafone SIM. They have both normal and micro SIMs. You can pick these up at any Vodafone store and usually at stores like The Phone Company or De Belwinkel. You will not need ID or anything. Just pay in cash and you are good to go.
Option 1: "Web+Sms BloX" - You want to add at least 15 EUR to your balance and then send a message to 4000 containing "web sms aan" to enable a 14.50 EUR/month 500 MB data plan.
Option 2: "Web+Sms+Bel BloX" - This one also includes more phone minutes and text messaging. You want to add at least 35 EUR to your balance and then send a message to 4000 containing "web sms bel aan" to enable a 34.50 EUR/month 1 GB data plan.
Both options include phone minutes too. Local/national calls are relatively cheap. Calling abroad will empty your balance quickly. I highly recommend SIP or Skype :-)
There are more options. I usually pick the second one because I also call a lot when I am in holland. If you just want data then the first one is probably cheaper. If you run out of data then you can simply add another 14.50 to your card and send the same message to get another 500 MB.
These options are described on this (dutch) page: http://www.vodafone.nl/mobiel_bellen/abonnementen/vodafone_blox/blox_voor_multimedia/
Last time I tried, tethering works with both these plans.
Data for iPad and Tablets
Vodafone has a prepaid tablet data card with 600 MB of data that sell for 7.50 EUR. You can grab these at the Vodafone store. You can pay cash. No registration or id required. If you do register on http://vodafone.nl then you get 400MB of data extra. This is a pretty good deal.
Last time I tried, tethering works with this plan.