Lido Cafe in Kensington (haven't been there for awhile though) Don't go through the back door and look at the kitchen though...
Nellies 'Secret Garden' on 17th is kind of neat too.
Best of all time has to be Btfsplks in Banff (50's Diner wise anyway):
http://www.banffpark.tv/joebtfsplksdiner.html