The most important (and expensive) thing you need is a good scrollsaw, and while the best do require a bit of investment, they are well worth the money.
Actually, some people make large intarsia with a bandsaw. It’s a really useful tool to have (especially if you’re cutting down larger pieces of wood), but you can’t get the detail you do with a scrollsaw.
What else do you need? If you’re just getting started with intarsia, not a lot actually: some wood (duh!), sandpaper, glue, your preferred finish – oh, and a pattern of course!
There are specific tools that can make your life easier – the bowsander is an example – and many intarsians go on to acquire a flexible drive like a Dremel for detail carving. These can be added as you become more accomplished or as fund permit.
Many woodworkers – scrollsaw users in particular – already have most of what they want when they take up intarsia. If that’s you, all you need is the pattern and away you go.
You might want a bit of help though
There are some excellent intarsia classes around, though they can be some distance away so that’s not always convenient. There are a number of videos at YouTube (and probably other sites). Most are free, so if one doesn’t quite give you the info you need, you can always try another!
Being a bit old-fashioned around here, we also like a good intarsia book. There are plenty available, and most come with patterns and step-by-step guides.
Anywhere else? You can probably find lots of online help through Facebook, Twitter or one of those other social sites. I’ll admit they’re not really my thing – shouldn’t be hard to find though! If you come up with anything worth sharing, give me a shout and I’ll spread the word.