1) Download the Modify Headers add-on for Firefox from here: http://addons.mozilla.org/en-US/firefox/addon/967

2) Add a new filter by clicking on the drop-down menu and hitting "add". In the first box, type X-Forwarded-For and in the second box, type in the IP adddress of any US web site. Leave the third box blank, and then save and enable the filter.

3) Next, block TCP and UDP port 1935. To do so on Mac, all you need to do is type the following in a Terminal window:
sudo ipfw add set 20 deny tcp from any to any 1935
sudo ipfw add set 20 deny udp from any to any 1935

Run "sudo ipfw set disable 20" to disable the rule or "sudo ipfw set enable 20" to enable it

This method should allow access not just to Hulu, but many other US-only streaming sites. Note that this may disable Flash on other sites, so you'll only want to enable this while you're watching video on one of these sites.

taken from lifehacker.com