This question comes up a lot, so here is the answer with links for more information and where to buy.
MacBook Air. I bought mine in early 2014, the latest version is priced from $1499. This laptop is still a delight to use, it's light and has an all day battery. If you're frequently on the go, consider the MacBook. Want more grunt for demanding tasks? Look at the MacBook Pro. Macrumors have a fantastic guide on the best time to buy a Mac.
Schools across Australia are using Chromebooks, they're great value, secure, easy to use and manage. They're also great candidates for business. Unfortunately in Australia, there is no supply of Chromebooks with a screen larger than 11 inches.
At work or university, if I had a MacBook Air or Dell XPS 13, I'd be a happy chappy.