Hello Mel
There really is only one CBD for Brisbane at present and that's in the heart of Brisbane (unlike Sydney which has North Sydney, Chatswood, Paramatta etc).
Depending on what you're looking for, "happening' suburbs close to Brisbane CBD include Newstead, Fortitude Valley, Spring Hill, Southbank, Kangaroo Point, West End, Tenereiffe, New Farm, Wolloongabba.
Brisbane's major public transport hubs is at Roma Street in the city. Bowen Hills is also growing as a transport hub. Brisbane Council is currently investing heavily in transport infrastructure with bridges, tunnels and roads being built at a giddy pace. Go to
http://www.Brisbane.qld.gov.au/BCC:BASE:1702902703:pc=PC_2468 for more information on Brisbane's development plans.
Mel, I hope this information helps - if you let me know what you're looking for specifically, perhaps I could steer you in the right direction.
Cheers
Heidi