low voltage 555 operation
Len's right, many parts will operate at lower voltages, there's just no guarantee that all 555's will. Try a CMOS version of the 555, like the 7555 or LMC555, if you want to run off a 3V supply. The high output voltage comes close to the positive supply (depending on how much current the load draws). CMOS 555s can't source much current, so you're better off sinking current when using normal LEDs (LED is on when the output is low - cathode connected to pin 3, anode connected to +VCC though a current limiting resistor).
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