Converting/scaling a voltage range ([0v - 5v] to [-5v - +5v])
For working with power conversions rather than signal -

You can use various integrated circuits for this job, they're commonly referred to as Dc to DC converters, there's also a range of ways to do the conversion such as Charge pumps.

Here's a bunch of different DC to DC converters they have various different current ratings, some step the voltage up, some step down and others convert between positive and negative values.

This is a nice charge pump IC that can double or invert a voltage with the minimum of external components. You could even use a 555 timer to convert a voltage to a negative

Hope this helps.