How do I keep sweat out of my eyes? Heading into the southern hemisphere spring I'm starting to contemplate another summer of having sweat running into my eyes and down my face.

I have a couple of lightweight headbands from Netti (that I can't find anymore) that have been reasonably good. They still get saturated on a long ride though and they're old enough that they're starting to smell.

There's an interesting thread here with some discussion around this area.

I've done some research and seen a couple of options:

Halo Headband

http://store.haloheadband.com/default.asp

Aside from the incredibly lame website they look like a reasonable option, with a fairly unobtrusive design and also the features to redirect sweat away from the eyes when they get saturated.

Sweat Gutr

http://www.sweatgutr.com/

This looks like it's very effective, but I'm not 100% sold on having all the sweat running down near my ears. Plus how would it fit with helmet and glasses?

Cotton Bandanna

The general opinion here appears to be that once it's wet, it's useless.
When wearing a helmet (and you're in Australia, so I assume you are) I almost always use an undercap, be it a classic styled cycling casquette, a skull cap or, in winter, a thicker beanie, perhaps with ear protection. 

In summer a casquette works well because I find that the sweat does form on the peak, but can then either drip off or evaporate more easily.