I was actually forced to go see Mamma mia here in NY...
ABBA are gods! I used when a student here in Manchester to go to ABBA Night (held once a month at a local club) where all they played was non-stop ABBA tracks - everyone got dressed up in last 70's early 80's gear - still the best vibe I've ever seen at a nightclub (and I went clubbing 3-4 times a week for 15 years so I've been to a few).
Same club did Smiths nights and they were great too ...