I like the mirrors at Z Gallerie:
http://www.zgallerie.com/c-63-mirrors.aspx

I don't know why I'm doing this for you, I'm seriously way too nice. Stay away from the armoires, I need one:

http://luckettstore.com/events/50-spring-market

Home Goods, for sure. I got a mirror there that is seriously awesome -- its gold and huge, with the old/mottled look, for $100. Saw it at decorum in Old Town for $485. Score.

They are also really great for storage mirrored stuff. I got our bathroom mirrored chest from there. I so should not be telling you this, because everyone thinks its from Horchow. As if.

Etsy?

some great online places for home stuff:

overstock.com, wayfair.com (no membership req'd, free or low cost shipping)
onekingslane.com, jossandmain.com, thefoundary.com (membership req'd)

home goods and marshalls have some decent home stuff but the inventory is constantly shifting so it's hit-and-miss

SOmething slightly distressed looking would be cool, maybe.

OP here -- style wise, I'm looking for something "transitional" -- not just a plain border, but nothing too wild either.

This is going back a while, but we got a really nice thick framed - I'll call it a distressed broze-ish material - mirror from a vendor who was always at Eastern Market in Capitol Hill on the weekends.

If you don't have time to go exploring though, I second Home Goods.

At the Restore. Find an old one and paint it or something.

Home goods

I like mirrors from wisteria and horchow.

Some more about what kind of style you're looking for?

Am looking for a small mirror to hang in my foyer. Any suggestions where to look, either online or in the real world? Thanks in advance!