Interesting wifi lists I've found:
http://v4.jiwire.com/search-hotspot-locations.htm
http://www.wififreespot.com/aus.html
http://www.travelpost.com/airport-wireless-inte…

Data is ridiculously expensive here across the board, especially compared to what I'm used to back in California. Most home broadband plans are expensive, data capped at low monthly usages, and then throttled down to 128kbps or lower once you've hit your cap. Free public wifi can be extremely hard to find, and when you do find it it's usually too slow to use. For instance, most McDonald's offer it, but in my experience it can be too slow to even update your blog, if there are a bunch of backpackers trying to go on Facebook and Youtube. Paid wifi at hotels and tourist areas is a huge ripoff too — often capped on both time AND bandwidth (e.g. $5 per hour or 50MB, whichever comes first).

The best option is to get a decent mobile plan and tether your laptop, assuming your device supports it.

Finding something that is “decent” for you can be tough. Cell phone coverage is big issue here, especially if you have any interest in leaving any of the big cities. Telstra has the best network around, and it's leaps and bounds better than the rest… but far more expensive. I have Optus which is completely decent in the cities, but even an hour outside of Sydney in parts of New South Wales with decent populations I was alternating between no service and one or two bars of non-3G.

Telstra coverage map: http://www.telstra.com.au/mobile/networks/cover…
Optus coverage map: http://www.optus.com.au/aboutoptus/About+Optus/…
Virgin Mobile coverage map: http://www.virginmobile.com.au/why-choose-us/ne…

A lot of the promotions that you've linked to seem to be new since I came over here. I pay $50/month for an Optus plan that includes 500MB of data, which is fine for me in the city now that I have broadband at home. While I was backpacking through cities and tethering every day I'd often hit the cap, and while I was backpacking through the country the service was too slow to make tethering worth it.

I live in Sweden and here you can get prepaid simcard with flatrate internet from many operators, telia, tele2, telenor and 3. I prefer “3″:

http://www.tre.se/Privat/Mobilt-bredband/DataPr…

199SEK for the package which includes usb modem and a SIM card (or micro SIM card if you want to use it in your iPad) and 7 days of internet

29SEK / day
99SEK / 7 days
299SEK / 30 days

I was in Germany a last year and there I bought a prepaid sim card from O2 and a few days of flat rate internet. I just went into one of their shops and asked for it. Can't remember the prices exactly, but probably like the deal from 3. Can't find a good web page, but it was sort of something like this.

http://www.o2online.de/nw/active/prepaid/prepai…

I was in Japan a few months ago and it was totally impossible for me to get anything. There is good 3G coverage at least in Tokyo where I was, so I didn't care about the other cell phone standard they had. Also, you would see people everywhere surfing the web on their phones, many iphones. However, since didn't live in Japan for at least a year and have a visum I couldn't buy these deals. The concept of pre-paid seems frowned upon or even unheard of. When I tried to explain the concept it sounded completely alien to them. Then again, I was speaking English and broken Japanese, so maybe anything I said sounded weird.

I tried to find out how to get 3G internet before I went there and I did find these pages if you want to rent an iphone or simcard. http://www.globaladvancedcomm.com/simrent.html and http://www.iphonetrip.com/ where the latter seems to be not only for Japan.

I mailed globaladvancedcomm to see if it would fit my phone (unlocked Nokia N900), but they said it was locked to the iphone (although they did not explain how that was possible). They also had not heard of any prepaid options.

However, apparently, everyone I talked to was wrong. A few days after I came back, I read this blog post

http://torum.net/2010/06/better-mobile-internet…

which pointed to an operator called b-mobile (which I had heard about, but not that specific offering). I haven't tried it, or can't vouch for the blog, but it sound promising and I will definitely try it, when I go back to Japan.

best of luck and may there be cheap internet everywhere for everyone