What flash is needed to photograph a reception?

Can you explain to me how good the flash would be? It will be used to photograph a reception and does it fit on the camera? Is it easy to take off etc?

For a Nikon D3000

Nikon SB-600.
It's strong enough with a tele range of 30m/98ft at ISO 100
This value often confuses people, so I will make it easier to understand.
First, on your camera is the ISO, it is how sensitive the sensor to light, so, the flash would be more sensitive to the sensor when set to higher ISOs, this flash, at ISO 200 has a range of 42m/138ft.
The tele range means that it can be set to wide angle or tele, which is just something like a switch to magnify the light, to change between wide and tele you just need to push or pull the head of the flash.
This flash is affordable, easy to use and of course fits on any Nikon camera unless you got those ancient DSLRs. It's of course easy to take on or off, it's just a small switch below

The SB-700 is a nice flash that won't break the bank. It is FAR easier to operate than the "perfectly adequate" SB-600 mentioned above. If you get deeper into wedding photography, you will appreciate the fact that the SB-700 can act as a master flash to trigger other units, too.

A speedlight and a Gary Fong Lightsphere.

SB600s have been discontinued, and those that are still available, for some strange reason, have seen a price increase to over $300.

I paid about $225 for my SB600. If you can find a new one for that, buy one.

But if all you can find is one for $300, get the SB700, which is only a few dollars more, and will give you remote commander capability, should you ever want to control other flashes (your D3000 can't act as a remote commander).