HP is now claiming 24 hours for one of theirs. (pricey)
My Macbook can do 4 hours no problem.
Not sure on the mini's.
Don't be misled with those claims from HP and Dell. The Dell laptop that lasts for 19 hours has a 9-cell battery which is rated for 9 hours, but needs to be partnered with a 12-cell battery slice which sits under the notebook. I'm not carrying around a 14" laptop that weighs that much. To me all of the netbooks are crap. I guess if you just want to use it for playing movies for travel. The 13" Macbook last for 5 hours and the new 17" Macbook Pro is less than 7 lbs and lasts for 8 hours. I agree with NudeDiver, if you ever try a Mac, you will never go back