There are a lot of filters and plugins available in web for great multimedia softwares like Photoshop .Here we showcase a collection of plugins and filters used in Photoshop software.
Looks as if this slipped through moderation as it looks like a website promotion to me. It wouldn't be so bad if this list wasn't out of date. Nikon Color Efex is a free Google Nik collection plugin now and they don't even mention all the other Nik plugins that are free. In it's day Knockout wasn't a bad masking program but today it's expensive at $100 and I'm not even sure it's still available from Corel. The OP has no posting history here so I expect it wasn't accidental a promo was posted.