help_haiti is a comm to which fandomers offer and bid upon fic, graphics, art, whatever with all funds going to Haiti. More eloquently, their userinfo states: This Journal was created in the morning of January 13, 2010, as a place for fandomers to help raise money to help in the rescues, recoveries and rebuilding of Haiti following the tragic earthquake on January 12, 2010.
There are tons of amazing offers, spanning many fandoms. And if you're able, please consider offering something up as well ♥ For those with a specific interest in Merlin, lamardeuse has an ongoing list of Merlin offers here. I haven't looked through them all, but there's definitely a very broad range of things and pairings offered.
For what it's worth, I've offered Merlin fic (thread here). Either a single fic of at least 3000 words, or a series of 400 word or less ficlets. Arthur/Gwen, Merlin/Morgana, Gwen/Merlin, Arthur/Gwen/Merlin, gen, RPF (Angel/Bradley), or crossover fic. Starting bid of $2 - every bit counts.
Also, Arthur/Gwen shippers, keep an eye on camelot_love as threemeows organizes an Arthur/Gwen specific thing-a-thon exchange for money going to Haiti.
ETA: A few specific notes to Canadians - if you have Bell or Rogers service, you can text "HAITI" to 45678 to donate $5 to the Salvation Army (Telus should have this service available within 24 hours)
Also, the Canadian Government is matching all individual donations made to Canadian charities towards Haiti. (Thanks, heather for letting me know! ♥)