Well, you know when you need a VPS when:
1. Your webhost contacts you about your resource usage.
2. You need a lot of space and bandwidth and you need it dedicated JUST for you.
or 3. You have several sites you want to consolidate.
I have several hosting sites bookmarked that have looked promising over the years, but I don't feel comfortable posting it in public (you know, I don't actually know about their services since I haven't ever used them before, but I've heard good things about them)
