Mt. St. Helens is at it again! The site of one of the most spectacular volcanic events in recorded history is heating up again. I remember the "big blow" of May 1980 very well: I was a wee Sea Scout, we were at the Regional Regatta at Sand Point Naval Air Station (on Lake Washington), marching back to the boat from breakfast. We all heard a loud "sonic boom" (bam-bam!!!) and looked for the offending aircraft. Shortly after that, at the church service, it was announced that all units hailing from the Portland area were going to have to find an alternate road home as the volcano had erupted and I-5 was closed where it crossed the Toutle River! Then, a year and a month later, we were having a little swim party in Liberty Bay (Poulsbo, WA), Sea Scouts again, when we notice a "mushroom cloud" going up to the south: it was the second, though not as explosive, eruption. We motored back to the dock and covered all of the air intakes on the boat in case the ash drifted our way (that stuff played hell with machinery). Luckily it only got as far north as Olympia.
Anyway...the P.I. has a good article on the current situation here. For the straight dope, go to the UW Geology Dept's page here.