We use mint.com, and have used it for almost a year (I'm pretty sure we signed up in February). It is totally safe and secure, and I love getting instant alerts through email and texting if we go over budget in any category.
Mint has helped us make a budget, track our spending, and set goals for future savings and paying off my student loans.
It also tracks your net worth over time, and compares your spending with others within the US.
I loooooooooooooooooooove it, and it's totally free!