I would highly recommend Minyon Falls walk. It is just outside Nimbin and is in Nightcap National Park. It has a great walk down to the base of the falls and back up the other side. The falls probably won't have much water flowing but they are a big drop (approx 50m) and the walk is about 7km long so a nice half dayer, beautiful rainforest down the bottom (we caught (and released) a beautiful blue rainforest crayfish).
Also search this forum site for "Sphinx Rock" - it is a distinct rock outcrop outside Nimbin but takes some walking, it's unmarked track and a bit overgrown I think as of last reports.
And there's the Nightcap track which is 16km long and follows the old postal horse route. I think that's a one way track.
See
http://www.environment.nsw.gov.au/natio ... x?id=N0062 for all the walks in the park.