LSD is indeed available in Amsterdam, but it is considered an illegal hard drug here, and anyone possessing it, especially in quantity is subject to arrest and imprisonment. Also LSD, while not addictive is a very powerful psychedelic drug with numerous physical and psychological effects. It's not for the faint of heart nor anyone with depression or other mental disorder.
Apparently much more of the LSD is being exported to places like Germany which has recently noted a ten-fold increase in LSD seized along the border with Holland.
Some of the LSD being manufactured in Holland is used locally by the club set who perhaps are finding Ecstasy to be less of a kick after continuous use. So you may be offered LSD in a club setting along with Ecstasy. Some of the LSD is available in sheets (blotter), but it seems certain labs are making it in a pill form, thus confusing it with Ecstasy, which also appears in pill form. BEWARE! Know what it is before you take it. The Dutch will know and will tell you (hopefully) if you ask.
Another warning - LSD is NOT a party drug! Although many younger, less experienced people will take it at a club, concert or party, they eventually learn it's way too strong a mind fuck to experience in an unfamiliar or crowded setting. In addition its effects last at least 10-12 hours during which time you will not be "yourself." For more info about LSD check out erowid.org, an excellent resource on mind altering drugs.
Last Warning - LSD is NOT available for sale in coffeeshops. And if you try to score from dealers on the street you WILL be ripped-off. Don't say you weren't warned!