Ontario 1-Call has recently (Spring 2010) updated their list of contacts for their member utilities.  You can get to that list by clicking member utilities.

We have some locate contacts on our website as well, that you can get to by clicking locate contacts.

We also have a printable pdf version that you can get by clicking on Printable Version.

Frontier Utility Locating Services has a good system on their website for finding the phone numbers for locate contacts.  You can select the municipality and see the phone numbers for contacts.  You can get directly to that system by clicking Frontier.