Here is a quick overview of my collection, the bulk of which is US games and hardware. I bought most of this back in 2001-2004. Then I took a break from dreamcast for several years, and now, since 2010, I've begun picking up some more stuff, mostly imports.
My main usage DC. A sega sports model with region free bios.
Imports: Japanese and European games.
US games, most of which were purchased back in the day.
My current setup (pic taken before Karous artwork applied to the DC):
Not pictured: spare dreamcasts, many normal controllers/vmus/web browser discs etc