1st decision is laptop or desktop.
Does your home have a wireless network ? Would it benefit from one ? (Let's you surf the web / check e-mail from any room or from the garden).
I highly rate the convenience of a wireless network. It changes how you use the computer.
I also quite rate laptops as I love being able to move it from room to room, go to a friend's / client's house with it etc. It also means less crap on the desk - just a power lead really.
Apple make a range of expensive laptops (silver coloured, called Powerbooks) and cheaper laptops (white, called iBooks). For general e-mail, surfing, word processor, digital photos and music, you're probably better saving money and getting an iBook. For video work / more advanced stuff a Powerbook might be a better bet.
If you intend to use the computer in one spot only, there are two models which you might like to look at: the iMac has a flat-panel screen which looks lovely, and integrates the computer behind the display. Super neat !
If that proves too expensive, or you just want to 'dip your toes' in the water / Apple juice then the Mac Mini might be something to look at. It is just the 'processor unit' - you'd need to buy / re-use keyboard, mouse, screen, speakers.
All Macs can take wireless cards (many are built in).