How many bowlers have broken the 100 mile an hour barrier when bowling in international cricket (ODI and Tests only)?
There was a rumor that Jeff Thomson of Australia was the first bowler to break the 100 mph while bowling in international cricket. Later Shoaib Akhtar of Pakistan clocked more than 100 mph in a world cup match against England.
Once Mohammad Sami had also clocked the same but later it was found that the speed gun might be wrong in that case. Brett Lee, Shaun Tait and Shane Bond are some of the bowlers who clocked near 100 mph but there are not enough evidence to support whether they have actually crossed this barrier(Most of the cases it was found that speed gun had problems and hence it showed wrong reading at times).
Just to add to @ACB answer:
Shoaib Akhtar was timed at over 100 mph and was the first bowler that has broken the barrier (I say first as Jeff Thompson was just a rumour!), but his pace was questioned along with colleague Mohammed Asif's, after it was discovered they had both taken the banned substance Nandralone, a steroid which enhances performance.
Therefore, it is widely considered that the pace either can bowl at was not genuine.
ESPNcricinfo has a list of the fastest deliveries in World cricket (please read the notes carefully), but it has not been updated for a long time. Of those deliveries. According to this list, Shoaib Akhtar broke the 100mph barrier in an ODI against New Zealand in 2002. Australia's Brett Lee failed just short, with a delivery clocked at 160.8 kmh in 2005.
Shoaib Akthar clocked 100 mph at the 2003 World Cup, and he was tested before the match too, its the same World Cup that had Shane Warne kicked out for taking performance enhanced drugs.