What's your budget? "Real" fluorescence is expensive on a real microscope (expensive light source, expensive filters). I'm with DrJ- buying used is probably a good idea. We've bought from places like DoveBid before (scientific equipment liquidation services) with good results- they come with a short warranty. Haven't used them since they got bought by another company, but they were great before. I've heard good things about those AmScopes on Amazon but never used one myself.
On our mammalian cell culture scope we've got an olympus DP-21 cooled CCD system- it was $5k new for the camera and the computer to run it. I conenct to the side-port on our Olympus IX51, but I'm almost positive you could go through the eyepiece instead (cheaper scope won't have a side-port). On ebay it seems the controller units (it's actually a full tiny pc) are going for about $500, and cameras are ~$1500. Our model is marketed as for brightfield only, but it actually works really well for fluorescent samples, provided they are of decent brightness. The biggest advantage of these CCDs is the ability to control exposure time, plus the dark noise as mentioned. But if you could get the camera part for cheap enough, this is an entire computer system for taking publication-quality images and videos. You need an LCD monitor, a flash drive to stick into the computer to saves files, plus a light source (pricey).
More interestingly, these days there are a lot of papers/projects from big microscopy labs with instructions to roll your own- arduino-based, LED excitation, etc, and most importantly, using your smartphone or a cheap CMOS as the detector. These drastically cut down on the cost versus a traditional microscope, which is sold at grant money pricing (basically add a zero).
- the CellScope is awesome: http://cellscope.berkeley.edu/
(http://journals.plos.org/plosone/articl ... ne.0096906
). Honestly, I'd go for this.
(details here: http://www.wormbook.org/wbg/volumes/vol ... mber-1.pdf
)- here you can rig a simple stereoscope for fluorescence.
- thingiverse has a bunch of 3D printable mounts to take images through the eyepiece with a smartphone instead of buying a point-and-shoot.
- imageJ and micro-manager are free, research-grade software packages for image analysis and instrument control.
- something like one of those could be a fun project that could span shop class, physics, bio, etc!
Also, if you're anywhere near a research university with an imaging facility, they love doing high school outreach!