I'm building a circuit that I'd like to run at 8 MHz to begin with, but I want to be able to try it out at 10, 12, 16, 20, and, maybe, 25 MHz. I know that many microcontrollers have the ability to just plug a passive crystal into two pins and the µC will generate a square wave and pass it on to anything else it's connected to which needs a clock. What I'm wondering is if that functionality exists on its own in a nice, small package which will run at 5V. (I know I can build it using Schottky fast inverters and some capacitors and resistors, but I'd rather avoid all that external stuff if at all possible).
Alternatively, is there an easy way to generate a continuous range of frequencies of this magnitude (similar to what you can do with a 555 timer at lower frequencies)? I'm not too fussed about the frequency being particularly accurate, I'm pretty sure a 1% variability would be acceptable (2% seems like it's pushing it, but I'd certainly be willing to try it out)
Additionally, I've seen a suggestion to use a higher-frequency crystal and use a frequency divider to divide it by four. Is a T Flip-flop the best way to do that at these frequencies? (or, rather, two since one flip-flop is only going to halve the frequency). Does this advice make any sense given that I'm running this on a breadboard? (yes, I know, parasitic capacitance and all that, that's actually part of the reason I'm doing this experiment, I want to see the effect of this parasitic capacitance at the various frequencies and to see whether mounting the breadboard on a grounded copper plate makes any difference)