http://www.F1today.nl
It has livetiming, well timing as it comes into the press conference hall so it may be each 15 minutes, or 30 minutes..
By the way on forums of autosport in the racing comments section/winter testing thread, you have times quite frequently cross checked and translation of live update from F1today.nl so pretty good.
today we even had a lap time chart for a lot of lap done by the pilots so you can see the consistency.