The ICL7660 is the old standard for generating a negative supply rail from a positive supply. It uses a switched capacitor arrangement and it can't supply much current but this is usually OK for op-amp circuits. There are other similar devices such as LT1054 and MAX1044. These are good if you need to generate a negative rail that is more negative than the negative terminal of your power source. Use pi filters on the input and output to avoid switching noise.
If you only need to split the supply, I recommend the Texas Instruments TLE2425 and TLE2426. The 2426 splits a supply in half, i.e. it generates a "virtual ground" rail half-way between the positive and negative supplies, so you could split a 9V battery into +4.5V and -4.5V; the 2425 splits the supply at 2.5V above the negative rail, which would give you +6.5V and -2.5V which is not what you asked for. These are suitable if your supply is isolated - for example if you have a 9V battery supply that you want to split up, and it's OK for your circuit's "ground" rail to be part-way between the positive and negative rails from the battery.