It's important to consider "total compensation" when evaluating a job offer and not just base salary. For example, if you are making $40,000 per year at your current company and you are offered a job at anoter company for $44,000, on the surface it looks like a good deal - a 10% raise in base pay. But before you leap, it's important to factor in the cost of health benefits, the amount of paid vacation and holidays, any waiting period on getting a match on your 401(k) contributions, etc. When you lay it all out there, it's possible that what appears to be a 10% raise is a wash.
There are plenty of tools available on the web to help you compare two job offers - here is one example and another. Be sure to factor in every possible benefit into your comparison. Ann Bares over at Compforce notes that a new benefit is on the horizon for workers in Japan - Heartache Leave. It's interesting to me that the older you get, the more time off you have available. And I thought the drama would settle down as we got older and wiser!