Mods, I'm going to write about both recorders and mics here--don't shoot me.
You don't have to worry about your recording withstanding noise from traffic, etc. Your recorder will reproduce the signal it gets from the mic--either the built-in ones or external ones. If it's loud enough to distort--say, a truck horn from a vehicle about to hit you, or jackhammers--you're not going to want to narrate from there anyway.
But you do need to make a decision about whether you want to record in stereo or mono. You've only got one mouth, obviously, so mono should be sufficient, but most small recorders have a stereo jack. That will record a mono mic to the left channel only, unless you get an adapter. Or you could get a stereo pair, which would be useful for more realistic ambience--NPR gets all those environmental sounds in stereo.
I have the Sony PCM-M10. I have not tried its competitors--from Tascam and Olympus--because I am very happy with it. The more knowledgeable electronics people here have praised its mic preamps as being relatively low-noise, so you will get clean recordings from any external mic. Its mic jack is stereo. But if your budget is under $229, you can probably get good voice recordings with something cheaper.
The Olympic recorders do record in mono, but beware--they record at lower fidelity in mono, and I would suggest using stereo instead. Check out Page 51 (or Search for mono) in the LS-7 manual.
http://www.olympusamerica.com/files/oima_cckb/LS-7_Detailed_Instructions_EN.pdfDon't clip any microphone under your clothes unless you want to record cloth rubbing against it. Remember, what the recorder hears is what the microphone hears. The microphone should be out in the open air.
I get very nice voice recordings (in stereo) with the Sound Professionals BMC-2.
http://www.soundprofessionals.com/cgi-bin/gold/item/SP-BMC-2 They come with windscreens, and because they are omnidirectional (not directional or cardioid) they are better at rejecting wind noise.
But you have other choices. Take a look at Flinstone's post from another similar thread
http://taperssection.com/index.php?PHPSESSID=dac2c7d0169a44be714cbf8a13ea4ec8&topic=146179.msg1881388#msg1881388