They are truly seasonal ales, as they can only be made at the time the hop flowers are harvested. This is usually in in August or September depending on climate.
Interestingly, while they are extremely hoppy, the flavor of fresh hops is quite different from that of dry hops. The beers made with them often have a mellower, herbaceous, grassy, and floral hop flavor instead of the biting citrus or pine character associated with dry hops.
Some West Coast examples of this style of beer are Deschutes' Hop Trip, Moonlight Brewing's Green Bud Ale, and Russian River Brewing's HopTime Harvest Ale.
There is an annual festival in Yakima celebrating fresh hops, called, unsurprisingly, the Fresh Hop Festival. This year it takes place on October 7.
I talked to the folks at Toronado last night and they are 90% sure they will be holding a Fresh Hop festival again this year near the end of October.
PS. I could have sworn someone started a thread here about a fresh hop beer; but, I'll be darned if I can find it this morning.
Edited by eje, 09 September 2006 - 06:01 PM.