I have a Canon 600D with twin lens kit and also 50 f/1.8. I'm looking at extension tubes to extend macro capabilities.
These on Trademe: http://www.trademe.co.nz/Browse/Listing.aspx?id=416139974
and these at ebay (current exchange makes them NZ$211.78: http://www.ebay.com/itm/New-Kenko-Extension-Tube-Set-DG-Canon-EF-lens-H192-/300558580982?_trksid=p4340.m185&_trkparms=algo%3DSIC.NPJS%26its%3DI%26itu%3DUA%26otn%3D5%26pmod%3D180659021654%26ps%3
There's also some cheaper ones on Trade Me:http://www.trademe.co.nz/Browse/Listing.aspx?id=416102869
From what I've read so far on various forums it's better to go for kenko or Canon "own" brand (although I haven't seen any Canon advertised here). Certainly I can't see the point of saving so little money between OEM brands going from metal to plastic connections. The question is OEM over kenko I guess.