What are some suggestions for a thank you gift for my daughter's coach?

something for in his garden, a tree or a nice plant.

a thank-you-tree! :P

or something else that will last, flowers/plants have lots of meaning to them. he will enjoy it for years to come, and everytime he sees it he'll get reminded of you guys!

Food gift cards are always a safe bet. Coffee shops are good, too (they always have other stuff like smoothies or hot cocoa if they aren't coffee drinkers). Everybody eats, so it will only be a matter of time before he could put your card to good use! I'd go with someplace basic, like Applebees or Perkins, or something, where his family can all get something they like. If you weren't planning on spending a lot, a $5 or $10 gift card to Dairy Queen, Starbucks or Caribou is a nice treat he could share with his family as well.

How about a really nice framed photo montage of great moments from this sports season, with a tiny engraved plaque "Thanks for all you do! 2009 team" or something similar on the bottom of the frame.

I saw a great idea of having the photo montage framed and matted with a thick white matte. On the matte, the girls could each sign their name and sports number and write a short note of thanks.

He will really treasure that for years to come.

Give him a gift card to a restaurant.

Movie passes for him and his family. Tickets to sporting event.

depending on the sport your daughter plays... eg basketball, soccer,volleyball, etc. Give him a signed ball. have all the team mambers sign it then give it to him and it will be sentimental