Single MaltsMost scotch is distilled from barley malt and starts out as grain neutral spirits. It is then aged in wood where it is allowed to interact with the cask and atmosphere and evaporate (the angel's share). It is during this aging process that the whisky acquires most of its flavor. Finally, it is thinned with local water (usually very soft water from a local stream) to bottling strength, which also adds additional flavor elements. The fun whiskys are the single malts, each of which has a distinctive taste. The single malts are used with grain neutral spirits and other less mature whisky's to produce the blends.
For the record, Lagavullin, Bowmore and Laphroaig are from Islay (isle-a) which is an Island off the west coast of Scotland. The malts there are usually smoked over a combination of seaweed and peat, and then aged in the sea air, giving them a very distinctive briny smokey flavor.
Also for the record, Bushmills is not Scotch but Irish and therefore a whiskey. Most Irish whiskey is blended but Bushmills does a single malt. I understand that Bushmills is owned by protestants, so you may want to be careful ordering one in Ireland.
If you have never been on a tour of a whisky distillery you should try it sometime. My company had a plant over there for a while, so I got to do a few tours. Very interesting and lots of free samples afterward.
By the way, the Scots usually drink their whisky thinned with only cold well water to taste (no ice). Usually your dram (a measure) comes with a small earthenware pitcher of water in Scotland so you can do this your self. Most people over there thin by a third or so. Drinking it straight burns the palate so you can't appreciate the flavor differences, and ice is for the (terrehable) Americans. Poland spring on any other good spring water works well for this purpose should you wish to try it.
Here are some of my favorites which are readily obtainable stateside:
Island Malts: Lagavullin 16 and Isle of Jura 16. Jura is light and well rounded, nothing like the heavy, peaty flavor of the Lagavullin, but both are very good. Isle of Aran 8 year old non-chill filtered is a great favorite, most whisky's are chill filtered to clarify them with removes flavor elements, but not this one. But impossible to find in the US.
Highland and Speyside: Dalmore Cigar Malt (12 year old?) aged in olorosso sherry cask for a distinct, mellow rounded taste. Balvenie Double Wood 12 year old, aged in once in bourbon and then again in sherry casks, again a nice smooth rounded dram with complex overnotes.
Lowland: Lowland refers to the area between Edinburg and Glasgow close to the English border. Lowland whiskys are usually lighter in tone with marvelous citrus notes, and are my favorite if I am having more than one. My special favorite here is Auchentoshan 3 Wood, but failing that anything from Auchentoshan.
Irish Whisky: Kilbeggan and Paddy, occasionally Tullamore Dew. Since these are blends age is usually not as much of a factor. Kilbeggan is distinctive and lighter in flavor than most other Irish whiskeys, so if you can find a bottle grab it an give it a try.