A couple of comments here.
1) PSF supports an ASCII mode which is pretty easy for creative coders to write to and the "psf" executable can converts ascii to binary and back if the ascii performance is not acceptable. Just take any psf file and run the "psf" executable on it and you will see the ascii output (% psf tran.tran)
2) PSF and SST2 are both proprietary formats also Cadence does as part of its OASIS simualtion integration to ADE provide access to writing PSF but you must purchase this integration kit to gain access. For newer formats like SST2, access is not provided.
3) I've shared in my feedback to the subject "How to plot a graph" (Feb09) the process of using "csv" files to import external data into WaveScan & ViVA XL as this is pretty simple as well as the option to use the calculator function "getAsciiWave".
4) If you have VCD data then you can easily convert to SST2 using the simvisdbutil exectuable that comes in the IUS (AMS) hierarchy.
Hope these options help,