Image via WikipediaI chose a Samsung HM251HI with 250GB.That's enough room for storing videos and plenty of music. After making a backup to a external HDD I simply replaced the internal harddisk of the PS3 with the new one.
Then, after booting the PS3, I had to format the drive and select to restore the data. How-to's for that are plenty on the internet, e.g. from Gamespot.
Now it's currently transferring the backup to the PS3 and this takes quite a time. With my 40GB free of 7.5GB it will take about 46 min. Wow. I'll let you know if it was successful after it's finished, or if I cry in rage about a defect/incompatible device.
Update: Yes! It worked flawlessly. Great. I expected the worst. It's Sony, you know. But this time, I have to admit, it couldn't have been easier. The Samsung HM251HI HDD is faster than the original one, even though it's 5400 rpm, too. And I got a valentines card and some nice words from a cute girl too today. Happy...