Where can you get a good mobile wifi hot-spot that doesn't charge monthly?

Free hotspots are available to customers at most good public establishments such as McDonalds and Starbucks. However you have to be a customer to use their internet, otherwise they can legally tell you to leave the premises, so, Just buy a drink or something if you go to a food/drink place for the WiFi.

You can also find them at airports, some libraries and some train stations.

In a public place, you can also search for unsecured internet connections that do not have a password on them. However be aware that the owners of the WiFi in these cases may be able to access details on your mobile device, such as who you are, and remotely shut down your connection.

There should be a poster up advertising that places have free WiFi for customers.

If you are in the UK, you can get free public WiFi with BTOpenZone.