Ideas needed for a fundraising trail ride to benefit a therepeutic riding program.

I think the raffle idea is a good one, on several of the local rides they have a reasonable fee for the ride and then a raffle to raise even more money. 

Sounds like you have a lot of great ideas! 
 
Our theraputic riding center is using kroger cards to earn money.  We all got these cards - they are like the kroger gift cars & we load money on them before we buy stuff at Krogers.  Its just one extra step - Like if you think you are going to spend $100 - then you load $100 on the card before they start scanning your groceries (or you can put even a months worth of grocery money on there, etc).  Then after your groceries are scanned in - you then pay with the money you loaded on the card.
 
However, Kroger keeps tract of all those cards and all of our "money" is credited to the theraputic centers account.  Once we collectively have spent $5000 (it happenes really fast when you have enough people buying groceries) then 4% of everything beyond that gets donated to the riding center. 
 
It doesn't cost us anything more - just the one extra step that really takes no time at all.  Our center charged $5 for each card because that is what was already loaded on each one - so pretty much an even trade.  In the first week they have over $1000 in the account.  You could have these available for the people in the ride.  Its a good long-term money maker for the center. 

Our 4-H group just had a silent auction where the families brought in stuff. Our goal was to raise $50 for cancer research. We made $300. This was just our club, about 30 people total.

Another auction idea is a pie/cake auction. Our FFA group did that this winter and raised A LOT of money. Every pie sold for at least $125 dollars. Some sold for $500 and one was resold 3 times for 300-500 each time. It was a fun event. The auctioneer had a great personality, which helped.

If you do your auction separate from the ride, you could also have a chili cook off and sell chili dinners or frito pies (pretty popular thing to do here in New Mexico).

I like the Kroger card idea. We do that for our elementary school. Its really easy.

That's a great idea, j_c!  I sorta like poker runs.....  Silent auctions are neat.   Ummm......  Bring a bag of feed and get..... something....  You could do grab bags and put in a curry, a hoof pick and some homemade horse treats and charge a couple of dollars.  Bake sale at the ride....refreshments, of course.  St.Jude always has rides.  They charge $20, I think.  You should advertise well at feed stores and newspaper and be sure there are no other major events going on.  Have a wagon to pull hill-toppers..... no-horse people..... charge them half price.

We *just* had a benefit ride last Saturday.  (for MS)
There's a nominal fee to ride, and then, if you want, you can buy a poker hand.  (These were $5 for one hand, or 6 hands for $10.00)  I've never won, so I can't tell you what the payout is!  LOL! (I feel like...I went there to donate...so that's what I do!)  Another big thing is 50/50 tickets.  If people know they have a chance at some $$$, they will spend.  There was also a goat raffled off that day.  (The goat was there, so people could see what they were getting....cute little bugger.)  Those tickets went for a buck apiece, and the goat was donated.  Last year this was a huge hit.  I couldn't tell you how it went this year.
I like the idea of 'silent auction' horsey items, too.
After the ride, we could buy hot sandwiches.  This was for the MS benefit, too....