Something like TNT

Not sure about tris, but a local cancer center that provides support for patients and their families is having a TNT-style training for a half-marathon here. The cool thing is the fundraising minimum is much less, so it would be achievable for me.

I know the Janus Challenge let's you pick your charity, but that might be Ironman only.

I did fund raising on my own a couple years ago for a colon cancer research - a disease that has been unkind to my family.... If there is an organization that you would like to raise money for, you can do it on your own. You can use a site like Firstgiving (http://www.firstgiving.com/) which allows your donors to donate on-line, but Firstgiving takes a percentage as an administrative fee), or you can use something like PledgPage (http://www.pledgepage.org/), and have your donors send their donations directly to your charity directly to you, and you can forward them on to your charity. This was what I did, because I didn't want to loose the admin fees, but I DO think the first-giving approach may be a little more user-friendly....