I tend to shy away from organizations which many times are corrupt and just keep the tithe money set aside in me wallet until I see a person with a need on the street. There's been a few times that I felt the unction to stop at the church you just passed and give to them so I do.
The important thing is to have a giving heart which wants to help others. And when we have a giving heart everything in the universe clicks into place. Once you help or pay the tithe or whatever, it's done and complete now so do not ever be anxious about they might not use the funds correctly and buy a Mercedes instead of a truckload of food, or he'll prolly buy liquor. Remember, that's not what you're there to do. It's out of your hands now and it's between them and God if they stole God's money, but...you gave with a good heart. Let God be responsible for His own finances, lol.
Giving on the street is great. There's not much shortage of people who could use a little help, and it bypasses all the red tape and appointments or paperwork that most organizations hand to these poor folks who need help. Giving on the street puts it right into the hands of he who needs it.