I came across this the other day. You usually have to pay, but they're doing a promo where you get one of their plugins (of your choice) for free in exchange for a Facebook 'like'.
Go to the blue link on their website: http://www.plugandmix.com/
The process you have to go through can be a bit iffy, it might not work on the first try. You also have to download the whole package (which takes some time) and then activate the one you want.
There's a bunch of stuff that looks like it's geared towards the guitar too. I got the leslie, but I saw a demo where the 'echoflex' sounded really good.