They all can work (well the ones with .biq files do and many .bix files as well, stick with the .biq files first maybe...). There is a separate link on troubleshooting and sometimes making the ModPacks and Senarios work on a Mac - but I've had 20-30 running without a hitch...
Try these for starters (a) really brilliant (b) the way Civ 3 should be
...a) Age of Imperialism 1895-1924 (the effort and total fun of this is awesome),
...b) Worldwide 1
lots and lots to choose from, like Warhammer 2.5 - seriuosly you have gotta grab this one as well...
Some LoTR as well.. too much, only so many hours I can stay awake to play....
After the total disappointment of Civ5, i'm really enjoying all Civ3 has to offer...
I could be here all day...