What are some nikon slr attachments and accessories?

I know attachments are gimmicky and stuff, but what kinds of attachments are there out there for nikon dslr cameras. Also, what kinds of accesorries are out there. I have the Nikon d3100 if that makes a difference.

You have flashes, filters, microphones, GPS units, and obviously, other lenses.

Nikon has answers:
http://www.nikonusa.com/...index.page

Lenses
Flash + diffusers & gels
Tripod
Remote shutter release cord
Filters: UV for protecting your lens and a circularly polarized filter.
Gray card if you need to have accurate color.

You are just on window shopping.

Most People who buy inexpensive camera, don't buy other expensive stuff like remote shutter release, battery grip, extra battery, UV filter.

So first concentrate on lenses. Lenses are more important than these accessories.

First of all Nikon D3100 is a good camera to have… Its a professional camera which gives awesome photography. Recently Nikon Launches All-New 24.2-Million Pixels D3200 Digital SLR Camera as well. So dslr cameras are pleasure to have. D3100 comes with with AF-S 18-55mm VR Kit Lens which gives better visuals. It comes with accessories like Rechargeable Li-ion battery EN-EL14, Quick charger MH-24, Rubber Eyecup DK-20, Camera strap AN-DC3, Body cap BF-1B, Eyepiece cap DK-5, Accessory shoe cover BS-1, 2 Ferrite core, View NX 2 CD.

http://www.infibeam.com/Cameras/i-Nikon-D3100-SLR-Digital-Camera/P-E-C-Nikon-D3100.html?id=Black

Knowing that it is a D3100 helps. The D3100 is compatible with the Nikon MC-DC2 Remote Release Cord. It is not compatible with the ML-L3 Wireless Remote Control (Infrared) that works with most other Nikon DSLRS.
There are several flashes that are TTL compatible. The SB400 is a nice little flash, but it is usually worthwhile to pay more and get the SB700, because its greater power and adjustability is often useful in doing bounce flash.