Is a Nikon D80 sufficient for a wedding photographer?

Right now I just have a Nikon D80 with a 18-55mm lens. I'm thinking of possibly getting into wedding photography.

Bonus points for what kind of flash component I should get for these types of events.

The D80 is a perfectly competent camera up to the level of wedding photography, however, the 18-55mm kit lens will be struggling, especially in low light. You'll need faster lenses like the 50mm f1.8, the 85mm f1.8 or the 24-70mm f2.8.

For flash, I'd suggest 2 options - Nikon speedlights (SB600 or higher) which you can fire off camera wirelessly using the Nikon CLS system (your D80 pop-up flash can act as a trigger), This will give you the advantage of a wireless system with TTL flash control.

Alternatively, if you're confident (& competent) at adjusting flash output manually, then cheaper manual flashes & radio triggers would work well. You'll also need to consider some modifiers (umbrella or softbox) to soften the flash - no good for grab shots, but ideal for the posed formals.

However, most importantly, one camera body is NOT enough for wedding photography, you'll need a backup body that can take your glass and work your flashes (ie D70, D80, D90 and up).

While the D80 and 18-55 mm lens are quite capable of producing professional images, before you start attempting to supply such services, you may want to work with a professional wedding photographer and learn how to be a wedding photographer.

Just from your question it is clear that you do not have a lot of experience using a fully adjustable camera and providing images on demand.

Here is some of the equipment that some of my colleagues, who are wedding photographers, use when shooting such events.

2 -dSLR's (one as a backup)
50 mm f/1.4 and 24-70 mm f/2.8
2 - SB600, SB700 or SB900 electronic flash units.
A flash diffusion device (like Gary Fong's)
Flash bracket to prevent red-eye
Four to six 4 gb memory cards
And of course three to five years experience as a photographer

It's not enough - you will also need the experience and skill necessary to create salable images.

For flash, you will want an external flash (like an SB600 or better), maybe with a battery pack (depending on how much flash you plan on using). Many wedding pros avoid using flash as much as possible.

Read a book on wedding photography and you'll see what I mean.