Not really. While I do try to modify the cadence, use of expressions, tone, etc. of my voice to distinguish between NPCs. As well, all squires/servants invariably have a certain pythonesque variation on the british accent.
Oh, and for my upcoming anglo-saxon-themed campaign, I'm going to make sure to actually pronounce names properly: Elfwine is 'aylf-weeneh,' Cynemund is 'kyeen-ay-moond,' etc. The result, of course, is that satisfying 'anything but english or french' sound (even though, technically, it's Old english).
And I shouldn't forget to mention that I do have a few fairly good mild, generic 'foreign' accents for people who aren't native speakers of whatever language they're speaking to the PCs in. The trick? Pronounce vowels the non-english way.
I should also mention that my players don't use accents, and they aren't put off by the ones I assume. That said, I don't use pythoneque french accents, extreme (or any) scottish/irish accents, or anything that 'native' english speakers really have, other than my 'squire voice'.