I'm definitely a proghead, and I could write thousands upon thousands of words about my favorite bands.
The Moody Blues, who arguably aren't prog (but nail the "attitude" so to speak) are what got me into less conventional music within a conventional structure--their 60s and 70s material is still some of my favorite music.
Iron Maiden (yes, I believe Iron Maiden has at least had prog elements since the first album) and
Dream Theater piqued my interest even more in 2005, and other metal bands like
Savatage and
Sonata Arctica, which also bear prog influences, kept me interested. So my journey to prog started with metal, which is pretty close: metal bands often tout unconventional song structures and technical skill, so I'd say metal and prog are at least cousins.
It wasn't until 2008, when I was browsing for information about
Symphony X's V: The Mythology Suite, that I stumbled on a
funny anecdote from Wikipedia: A fellow prog band on the same label had released an album around the same time, also called V, with a very, very similar cover. The band was called Spock's Beard.
Spock's Beard? What kind of a name is that? I had to hear it. I promptly bought V, and was greeted with this:
[video=youtube;pidj1rhZdXg]http://www.youtube.com/watch?v=pidj1rhZdXg[/video]
I couldn't believe what I was hearing. If I could write music, this is what I'd write. I spun the CD until it didn't work and purchased the Beard's whole discography--not one bad album. Amazing. I began to expand my sights into other bands, including Genesis:
[video=youtube;SD5engyVXe0]http://www.youtube.com/watch?v=SD5engyVXe0[/video]
Kansas:
[video=youtube;qOVxNppbvBc]http://www.youtube.com/watch?v=qOVxNppbvBc[/video]
and
King Crimson,
Rush,
Yes,
The Flower Kings,
Marillion and
The Dear Hunter.
I have more to say, but I'm short on time. That's an introduction, and only an introduction, to some of my favorite prog bands. It's most of what I listen to now, because prog can contain elements of every genre, but it can also maintain the accessibility of rock and pop.