If you really loved a vendor, the most helpful thing you can do for them is post a rating here, on WeddingWire, and on Yelp. Lots of people decide to hire vendors based purely on a quick skim of ratings on one of these three sites. The more reviews a vendor has, the more visible it is on these sites. So the best way to thank your vendor is to post a good review and drive more business to them!
(This is NOT meant as a jab at any post or user! I was inspired to post this because I've been researching vendors lately and found one with a lot of happy posts in this forum, but not a lot of reviews on the above sites!)