I'm a teacher, currently in a role where I support other teachers in our district with math and technology. I'm involved in a technology demo class where they have class sets of iPads and iPods. In that case, I got the teacher everything he needed to connect one of the iPads to both a projector and a TV.
The projector doesn't take much time to set up, but it would be much better if you had your own, even a small portable unit. You can connect an iPad through the Apple Composite Cable, but any app you use would have to support "TV Out". More expensive projectors and TVs will have an HDMI connection and then you could use the Apple HDMI Connector and the iPad Display Mirroring feature to show anything that appears on the iPad screen.
If you want an iPad for yourself, you can also use it in class. If you are just thinking of trying one out for school, I suggest you try to borrow one, either from another teacher or even a parent of one of your students. There might also be technology grants available for your class, school, or board. Apple has lent my organization class sets of iPads for training, but I'm not sure how we got qualified for it (I took over the project at the point where I had to ship them back).
I can say that having an iPad or even iPod in the classroom can make a huge difference in spontaneity during a lesson. It also increases student interest in whatever you are doing. In elementary classes, I can get kids to do math problems until I make them stop just by giving them an iPad or iPod with a "worksheet" app! They love the immediate feedback. If you school has wireless Internet, it can make looking up a fact or word a matter of handing the iPad to a student who asked the question. I love handing a group of kids an iPad to watch a video... they pay so much attention and often rewind it to rewatch parts. It beats rolling in a TV/DVD player and having them sit while you get it started up... It changes learning from a passive activity to an active, student-controlled experience.
Using your own iPad in class is a bit of a risk, but I haven't had any problems at all in 18 months and hundreds of students. I routinely let kids use my personal iPad and iPod in class and I've never had a problem or concern about loss or damage. I do have to wipe it down thoroughly after the Kinders have been playing on it


. I make the younger kids sit on the floor to use it.
Let us know if you try it out! If you have more specific questions, feel free to ask here or PM me.