It'll be great to see some of your pics from Oz Roo. I look forward to that.

Hoya Circular filters are pretty good to be honest, you won't go far wrong with them on the front of any lens.

As Roo says, the best quality filter possible. Some of the cheaper ones cause a bit of chromatic abhoration. Also, try not to layer the circular filters too much as they start to cause a few problems, firstly deteriation in picture quality, secondly they will start to vignette with the shadows off the filter rim. The second is worse on wide angle lenses.