I'm on the Board of C2D2 and we needed a mailing list application that could provide for a full bi-lingual (French/English) e-newsletter blast. In my research I could not find any hosted mailing list services that advertise support for multi-lingual email marketing. That said, I did find some acceptable solutions...

PHPlist - a free open source application with internationalization (aka multi-ligual) features. I've used this tool with success before, but getting appropriate support and hosting (that won't be blocked by spam filters) requires further investigation.

CiviCRM - another open source tool designed for campaign management with extensive features for tracking online and offline communications with a mass consituency. I can't vouch for the mutli-lingual support but there are people in Ottawa working who may have some success.

MailChimp - is an affordable and very easy to use hosted bulk email tool. Although they don't advertise muti-lingual support, they provide options to customize what seems to be every element of system generated content, so you could make it bi-lingual from the subscribers perspective. See an example by the Canadian Education Association

Many other mailing list providers (e.g. bettermail.ca, ConstantContact.com, icontact.com) have options to customize many fields, but often there have exceptions like the subject field for 'welcome' emails that are autogenerated with hard coded English.

If you know of any better suggesitions, please post it in a comment below, Thanks!