Gantt Project - http://www.ganttproject.biz/
Cross platform, open source, and imports Project files most of the time.
The interface is a bit quirky but if all you're doing is creating basic stuff it's fine and I like it better than most of the other things I looked at, though I'll be honest, there's not a lot out there that's FOSS.
It supports assigning resources to tasks, dependencies, notes and custom fields for tasks, very basic resource management (including holidays).
Certainly if you're not a hardcore MS Project user it's got most of what you want and most of the stuff it doesn't do MS Project is a questionable on (cough resource levelling cough).
It's biggest weakness is that it's reading and writing of Project files isn't entirely reliable. For the most part the important thing with project files is to be able to read them when you're sent them (if you need to distribute plans you can send out PDFs and most people are fine with that). If this is a big deal for you then I'd suggest Gantt project for creation and investing $30 or so on a fully supported MS Project viewer to give you the security of knowing that you can read whatever gets thrown at you.