I don't go to church anymore. Well, not the kind of church that springs to mind when I type the word. I don't go to a building with a pastor and lifegroups and a preach and a pre-preach about how much blessing you will recieve if you give 10% of your salary. I used to go to a church like that but now I live with in a much more organic group of believers. We don't have formal meetings and we don't talk about God all the time but we do grapple with how to live as Christians a lot in a world where it often seems Churches are more intent on building business empires then pointing people to Jesus.
Since I don't go to Church anymore I've had to think about tithing. How it fits into Christian life and what God wants us to do with our money and our possessions. I figure since God actually wants our whole lives he wants 100% of our money and possessions too. Which can be come a little challenging when you realise that he doesn't want me just to give 10% of my (gross or nett) income away but he wants it all. Bye, new clothes every month, or fancy dinners out, since God can see other uses for it like clothing the poor or feeding the hungry (Ouch-even as I type this I know how far I have fallen).
For a while after I stopped going to church I would give some money away each month to various organisations I thought did good work with the poor. Then I started asking, "God, what do you want me to do with my money?" That's when things started getting a lot more interesting. These day's I don't give one lump sum to any organisation but I do find God encouraging me to be a lot more generous in my daily living. When I put a tip down for a waitress I'll feel him prodding me, telling me to give her a ridiculous sum or to buy diapers for a stranger in a supermarket or a meal for a homeless guy on the side of the street. These interactions with real people are a lot more valuable to me and my relationship with God then giving a sum of money (usually via EFT) to a group of people in a church who use 90% of it for lights, water and rent.
I'm not saying you should or shouldn't tithe but I would be interested to hear your experiences and what works for you.