Does anyone have a good listing script/software they use to integrate with their website?

We currently use a custom built one, but is a bit outdated with all the mapping technology, etc out there... so wanted to see what others were using.

Obviously this is just for our listings, not linked into IDX. For us, flexibility is key as we want to seamlessly integrate into the site.

Thanks! Look forward to hearing what others use (and if you showed a link, that would be great).