I'm actually going through that right now. I've always been a more "natural look" girl, and so lately, instead of foundation, I'm all about some concealer, pressed powder, mascara and lipgloss, and that's fine with me. During the summer, since I live in Texas, it gets SOOOO effing hot that my makeup literally melts off my face anyways, so I usually don't wear makeup during the summer, unless it's a tinted moisturizer, and even then, that's only when I'm going somewhere where I have to look somewhat presentable.
Also, this is kinda weird, and I might be the only one that does this, but if I'm going to the mall, I generally don't wear ANY makeup, because I know I'll be hitting up the makeup counters, and it's a hassle to take off all my makeup first when I am in there. I have been blessed with really great skin though, so I don't look horrible or anything.
I actually NEVER wore makeup excpet for aobut 3 or 4 times a year for about 6 years straight, because I was very very heavy (about 220 pounds on a 4'11" body) and I just stopped caring about how I looked. I've lost over 110 pounds now, and so now I'm making up for lost time by actualy geting up early, doing my hair, makeup, and dressing nicely. It's a nice change from wearing no makeup, sweats, and practically unbrushed ponytails for years and years on end.