Maxim have an extremely expensive one that goes up to 20MHz, MAX038.
EXAR had theirs but don't make it anymore.
I made and have 3 sine-wave generators:
1) A Wien bridge with a calibrated frequency dial and a dual tuning capacitor from an old tube (valve) AM radio. Its output bounces when the frequency is changed and its response drops off a bit at both ends of the dial because I couldn't match its 40M resistors and capacitance of the range switch very well.
2) An extremely low distortion oscillator that I designed to have a variable frequency, but its PLL caused phase jitter that ruined its low distortion. It has a CD4018 as a stepped sine-wave maker followed by a switched-capacitor 4-stage Butterworth lowpass filter IC.
I now use it with a fixed frequency but its frequency could be changed with a single pot with a switch selecting its decades. Its distortion at the high end of each range would be fairly low.
3) A phase-shift oscillator with a very stable output level, fairly low distortion and frequencies from 20Hz to 2kHz, and 200Hz to 20kHz. I had to use a triple gang pot from a RadioShack thingy and luckily it had 4 of them for me to select the one with the best tracking. I had to order a fairly high frequency (37MHz GBP) MC33077 dual opamp for it 'cause an MC33172 opamp had way too much phase shift at 20kHz. Even an MC34072 wasn't good enough.
Fairchild has a fairly new sine-wave generator IC. Its output supposedly looks like and sounds like it has very low distortion but measuring it shows its conflict in its phase-accumulator. Its output is very stable.
Interested in a schematic?