Programs that will handle conversion from mid/side to L/R stereo?
 

I've been reading up on mikes, it seems like the mid/side system has some useful advantages. However, it looks like you need to either a) process the m/s signal to L/R in the mike (in which case advantages are lost) or b) process the m/s signal to L/R in post, which lets you manipulate the soundfield.

Most of the software I have seen can only handle L/R sound. What systems are out there that let you make the most of mid/side recordings?

There are a number of VST and DirectX plugins available that will do mid/side to stereo encoding and decoding. One outstanding example is the professional quality Waves S1 Stereo Imager.

Another method to do it in any NLE doesn't need any plugins. It's especially easy if your NLE supports submixes or mix buses but even a conventional multi-track mix to stereo will do. You start with your 2 original mono tracks, one recorded from your mid mic, the other from the side. Duplicate the side track to a third track, select the copy, and invert its phase - almost all audio programs I've seen except the most rudimentary have a phase inversion effect - I'd be surprised if your's didn't but if it doesn't have it you can get it in the downloadable freeware program Audacity (a must for your collection no matter what other audio programs you have, IMHO). Initially set the levels of all three tracks the same. Set the pan controls so the mid mic is centred going equally to both output channels, the first S track is panned full left, and the inverted S track is panned full right (assuming the positive 'front' side of the figure-8 mic's pattern was facing left when recording). By adjusting the level of the mid mic track in the mix you can control the width of the soundstage while playing with the individual levels of the 2 side tracks can actually change the apparent direction the axis of the mic array was facing etc.

This is an especially good technique for video and broadcast since it collapses to mono without any serious phase artifacts, unlike the more typical A/B spaced pair or semi-coincident arrays a lot of people use. On the other hand, if you're going to 5.1 surround you've got all three front channels right there since the mid mic all by itself would become the centre channel while the two mixed channels would become the front left and front right respectively