The absolute best, most of the time, when the speech needs to be captured but microphones can't be in the shot, is a shotgun on a boom operated by a competent boom op, into a high quality recorder. The benefit here is that the boom op can move the mic to the speaker, alternating through the dialogue. (This is really tough!) If the mics can be seen, then a proper handheld is preferred, or a lav. A step down from there would be a mounted shotgun on a stand or similar, but if your actors are moving then you'll get weirdness as they pass in and out of the pickup pattern. Camera-mounted is the same, but then you become more likely to get sounds from the camera and its operator(s). A step further down is a bare stereo recorder like the zooms/etc. using its stereo mics. The problem here is for them to sound good you need to get close, which can interfere with your shot. They'll also pick up a lot of background noise and reverb.
So the question you should be asking, first, is "how important is sound" followed by "how much sound budget do I have?" The first question is really dependent on the content of your video. If you're shooting, say, a car show, then sound isn't typically as important as a one-on-one interview. That same question will help you determine just what kind of equipment is going to be OK -- for example, you could do the car show with just a Zoom (or even on-board on a 5D2 with AGC turned off) but for the interview you'd want something better.
One thing to consider is if there are rental companies near you. Most large cities have at least one pro AV/Film rental place, which can get you a good field recorder, mic, and boom for say $75 to $100 for a day. If you are only shooting for one day, then there's no need to sink tons of money into gear that won't get used often.
Now, what I assume you're really asking is what would be the minimal setup you'd want. This is really budget-dependent, and the sky's the limit in that department, but here's some standards:
1. Pro setup: Sennheiser MKH-416 mic, Rycote Windshield (kit 4), K-Tek KEG-100 boom pole, Sound Devices 702, porta-brace.... about $5k.
2. Not-so-pro setup: Rode NTG-3, Rode Blimp, Rode Boom, Tascam DR680, case... about $2k.
3. Acceptable setup: Rode NTG-1/2, Rode Blimp, tascam Dr-100... about $1k.
4. Cheap setup: Rode VideoMic Pro, Sony PCM D50... about $500
5. Budget setup: Rode VideoMic into camera.
Every step also needs headphones, cables, etc.
Of course there are a million other ways to configure each of those steps, but I'd say in terms of quality-to-price ratios those are about where everything stands.