I do donate, but I don't have a budget line for it. It was probably less than $1,000 in 2012, though. I also donate time, although it's sporadic.
As someone that works at a nonprofit, I urge everyone to take a look at your intended charity's 990, which is an annual filing with the IRS. There is a lot of... leeway in how one fills out 990s, and honestly, much of it can be opaque. But take a look at the hard numbers. How much is the executive director making? Are Board members being compensated (this is unusual)? Are Board members and/or executive staff also receiving compensation from related organizations? What was the filing year's deficit or surplus? How much information does the nonprofit disclose about how they spend their funds? I've seen three-word answers and three-page answers. Which one satisfies you?
All 990s are publicly available on Guidestar.org, although you need to register (it's free) to access them. Charity Navigator has its own ranking system, but taking a look at the data yourself is the only way to, well, know for yourself.
My favorite kind of volunteer work is working directly with people, but I don't really get a chance these days. I used to work exclusively in nonprofit fundraising, so most organizations wanted help with fundraising, not program services. Oh, well. You do what you can.