PS! This article is about Norwegian wireless broadband's, but you might find similar solutions in your country.

A couple of years ago I considered buying a subscription for a wireless broadband from ICE to use when I was out traveling or at our lodge. ICE uses the old mobile network in Norway (NMT 450) at 450 MHz which had and still has a great mobile coverage in Norway (though not used for mobile phones anymore). This network has a max down speed of 3,1 Mit/s and upload of 1,8 Mbit/s. However, at the time the subscription was too expensive (around 400kr/$80/£50) per month. It was not an option to have both a fixed broadband at home and the wireless subscription on top of that. Recently though they have started to offer a different subscription based on usage. Or actually it's a subscription where you pay for one week at the time, which is more attractive but still quite expensive if you're just using it in the weekends. However, having this as an option to get on the Internet when you absolutely have to is of great value. DinSide.no has an article about ICE.

Another company offering a similar concept is Telenor. Telenor offer wireless through normal GSM network (EDGE/3G/Turbo-3G). They has several subscription options from monthly, weekend to just usage. You can find more info here. There's also a test by DinSide.no here.

A third company (NetCom) also provide this service. Their subscription services is very similar to Telenor's, except they don't offer usage only.

Common for all of these is that you'll need a USB modem that your provider will provide as part of your subscription. Some providers let you use your mobile phone or your PC modem with a SIM card instead.