Waves J37 Tape

This is a good quality software. It simple to use, has a bunch of presets and most of them are quite useful.
Honestly speaking, there is no real tape saturation in this plugin, obviously, because it's not a real tape machine. =) But, still, it's a very good way to make your sound little more vintage. In a good way. ;-)
And, of course, this is a very versatile plugin. I use this plugin to add some vintage style tape delay to voice, or make sound of some instrument more smooth and warm. Or, to add some "analog" noise to my final mix. Or even use some crazy effects like shimmering delays or reverbs. Not as useful as a good digital plugins, but we are at the old school territory ;-)
There is only one serious minus: it requires a lot of computing resources and you must have a very powerful workstation to use this plugin on more than 10 tracks at the same time.