I found the following website on my travels. According to the site, this is the worlds oldest paddler steamer still in scheduled service.

http://www.skibladner.no/engelsk/index.htm

Regards
Eddy

SKIBLADNER is the oldest paddle stamer in the world in regular scheduled service, that is correct.
TUDOR VLADIMIRESCU in Romania is two years older, but only operates specail VIP trips, as far as I am aware.
Both will be beaten in, or around 2009, if and when RIGI, British built from 1848, returns to service on Lake Lucerne.

I know PS Adelaide of Australia to be the either third or first oldest "wooden hulled" steamer in the world built in 1866 I do believe

Adelaide is the third oldest "Wooden hulled" steamer in the world and was built in 1866