This is a great project. My son's class did it last year and the Disboarders were fantastic. I went on the UK and Canadian links and they all responded. I emailed all my friends and asked them to help and forward the info to their buddies. I contacted sports teams (guest relations) and they all responded, along with the most Governor's offices in the country, US Embassies and Consulates. One of the most beautiful responses came from the US Embassy in China, where they sent the class a lot of information and the Consule took the time to send an email and tell them about his job and the history behind the province.
The one the kids loved the most - Steve Irwin of Australia (THE CROCODILE GUY) who sent photos, calendars and stickers.
Go wild - use the internet to your advantage. A lot of companies - all over will respond. Just make one generic email and then past and copy to all their email areas. My son got thousands of cards.