MICROPOWER C-MOS OSCILLATOR, DRAWS ONLY 0.5uA  
If truly low power oscillators interest you, this circuit draws a mere 2 microwatts (500nA) from a 6v battery. It uses a very inexpensive C-MOS IC to produce a frequency of 2Hz. However, by changing the component values you can push it to 300Hz. The circuit draws much less current than traditional C-MOS oscillators using a Schmitt trigger inverter. It also produces fast leading edges. However, if you need more drive current, a C-MOS buffer should be included. Published in EDN, September 2, 1993.

VERY LOW POWER GATED CRYSTAL OSCILLATOR  
The circuit gates the output of a continuously operating 32KHz crystal oscillator to the input of a C-MOS buffer when clock pulses are needed. The technique gets around the problem of a slow starting crystal oscillator by keeping the oscillator going and switching on a transistor power stage only as needed. The method keeps the standby power consumption to a very low 1uA when used with a 3v supply.

D-FLIP/FLOP OSCILLATORS 
Yes you can turn flip/flop ICs into low current oscillators. This schematic shows you how.

200MHz400MHz VOLTAGE CONTROLLED OSCILLATOR
If you need a clean emitter coupled logic (ECL) type signal between 200MHz and 400MHz this circuit works fine. It uses four voltage-controlled capacitors to change the frequency.

PRECISION ULTRA LOWER POWER OSCILLATOR
This circuit works much like the classic 555 timer, but draws only about 1.5 microamps from a 3 volt battery. It is highly stable under varying temperature and supply voltages.

VERY LOW POWER ASTABLE MULTIVIBRATOR
This classic circuit draws only 200 nanoamps from a 1.5v supply.

CMOS INVERTER PARALLEL LC OSCILLATOR
I have used this parallel resonant LC oscillator circuit countless times.  The oscillator frequency is determined by the inductor and capacitor values.  I have shown an adjustable inductor to make it easy to set the frequency to a specific value.  Once set the frequency is fairly stable over supply voltage variations and temperature changes.  The values shown are for 125KHz but the frequency can range from tens of kilohertz to tens of megahertz.   With a 74HCU04 type inverter, it will oscillate down to about 1.5 volts.  If the frequency is low, you can also use a 74C04 (CD4069) inverter.

CMOS INVERTER 125KHz LC OSCILLATOR
This circuit uses a single CMOS inverter to form a series resonant LD oscillator.   The values shown set the oscillation at about 125KHz buth other frequencies are possible by changing the main LC values.

MEDIUM POWER 125KHZ OSCILLATOR
This circuit is similar to number 117 but adds more invertors in parallel to deliver more power.  The values shown are for 125KHz.