Hej
Hi / hello (most common; works in most situations)

Hej hej
Hi! / Hey! (friendly, casual)

Hallå
Hello? (often on the phone / to get someone's attention)

God morgon
Good morning

God kväll
Good evening

God natt
Good night (said when going to sleep)

Hur mår du?
How are you? (informal; about how you feel)

Hur mår ni?
How are you? (formal or plural)

Hur är läget?
How's it going? / How are things? (common, informal)

Bra.
Good.

Ganska bra.
Pretty good.

Så där.
So-so.

Inte så bra.
Not so good.

Jo då.
Yeah, I'm fine. (often reassuring; a very Swedish-sounding response)

Trevligt att träffas.
Nice to meet you.

Välkommen!
Welcome! (to one person)

Välkomna!
Welcome! (to more than one person)