I really like the small Dinotte lithium lights, reviews here:

Tail light: http://www.crazyguyonabike.com/revie...hread_id=41513
Head light: http://www.crazyguyonabike.com/revie...hread_id=41514

The tail light is particularly impressive - I once had a car driver get out of his car at a traffic light to ask me where I got it, he was so impressed. I'd say it's probably one of the brightest lights out there, hands down - very visible even in daylight. The only thing about them on tour would be that you need to carry the charger for the lithium battery, and of course find somewhere to charge it. There is also an AA version, but I didn't like it as much - the battery holder was not at all water resistant, nor was the connector. The Lithium version lasts longer and seems more weatherproof to me.

Dinotte also makes some larger versions with multiple LEDs - I have one called the 500L, which doesn't seem to be on their website any more, but it is even brighter than the small 140. But I think the small version is probably enough for most uses, and light & small enough to consider taking on tour. One downside I have noticed is that if you leave the battery plugged into the light for any length of time, then the battery becomes drained, so you need to be careful about that. But maybe they've fixed that now - last time I got lights from Dinotte was back in 2007 now. Overall, great lights, highly recommended, especially for commuting. For touring I might just take a battery blinky such as the AAA powered Planet Bike Superflash instead, since it's smaller and lighter and I don't ride that much at night time on tour anyway.

http://www.dinottelighting.com/

All that being said, though, I think that for the best visibility, a bright yellow jacket works better than any light. I've noticed when driving that I notice the flourescent yellow jackets way before any little blinky light.

Neil