From the BBC:

Laos: Barack Obama regrets 'biggest bombing in history'

It's good that Obama is expressing regret over this.  And it's good that the U.S. is finally donating money to help clean this up.

But, if you'll excuse the perpetual pessimist in me, I think the striking thing about this article is that for 50 years this went unacknowledged.

The statistics in this article are pretty heavy:

Eight bombs a minute were dropped on average during the Vietnam war between 1964 and 1973 - more than the amount used during the whole of World War Two.

...

Ten of the 18 Laotian provinces have been described as "severely contaminated" by unexploded ordnance (UXO).

The Convention on Cluster Munitions bans the stockpiling, use and transfer of virtually all existing cluster bombs, and also provides for the clearing up of unexploded munitions.

It has been adopted by 108 states, but not the US which, according to some estimates, spent as much on clean-up efforts in Laos between 1995 and 2013 as it spent in three days of bombing during the war.
The number of casualties from air-dropped explosive devices - mostly cluster munitions - in Laos since 1964 is estimated by the Landmine and Clustering Munition Monitor to be around 50,000 people. Of these about 29,000 people were killed and 21,000 injured. The overwhelming majority were civilians.

...

"Before the president's announcement I feared that the UXO operation in Laos would take hundreds of years," Mines Advisory Group country director Simon Rea told the BBC from Vientiane. "Now I am optimistic this can be reduced to decades."