You can use your GAL via LDAP with any LDAP-compatible address book. I use mine with both Outlook Express and Thunderbird. The address book is not browsable (you have to search) but auto-complete of addresses from LDAP works flawlessly in T'Bird. . .in OE auto-complete isn't quite as good as it won't show till the message is sent but you can search any address from the GAL using the "Find People" option.
The only trick (for me at least) is that I had to point the address book to the ip address of the server, for some reason it doesn't seem to be able to resolve the name on DNS. Then you have to put the correct information in the "base DN" field. For example, if your GAL domain is mydomain.com, then the Base DN string will be:
Code:
ou=people; dc=mydomain; dc=com
Post back if you have issues with this.