Speedlight for nikon D3100?

Hi can you suggest a speedlight suitable for Nikon d3100 and also a filter
thank you

Added (1). @deepblue 2 thank you your answer helps a lot. I'm thinking a Yongnuo YN 560 manual flash for my camera since i want to do learn doing light manually. If i stick to that, as you said i will need to get the flash off with radio triggers right?
about filters a uv will do to protect the lenses and also a filter to reduce lightfor that a neutral density wlil do the job?

The Nikon SB700 is a good one. The only filter I use is a UV filter to keep the lens glass clean and protected.

You have three main choices - either go for a Nikon speedlight that has TTL (most expensive option), a third party brand that has TTL or a fully manual flash (cheapest option).

TTL means that the flash can meter & set the power output - its basically Auto mode for flash. It's ok most of the time, but like most things Auto it doesn't always get it right.

I would recommend learning to light manually - not that hard to do & you at least get consistent results each time.

I use a Yongnuo YN 560 manual flash - about £50.In contrast a Nikon SB700 costs around £250. Also, your camera does not support Nikon's wireless AWL/CLS system in that the pop-up flash can't act as a commander (which might be one good reason to stick with Nikon, if your camera was compatible, or you later upgrade to a compatible body).

Whatever flash you get, if you are going to use it on camera (not the best place) then at least make sure the flash head swivels/tilts ti allow for bounce flash. Preferably get the flash off camera with some radio triggers (I use RF602's - about £20 a set).

As for filters - what filters do you want? I use UV filters on my lenses as front element protectors - Tiffen or Hoya are good makes.
The only other filters you need for digital photography are neutral density (and) or and grads for landscape work and maybe a circular polariser.

Edit>: The yn560 can be used on or off camera. IF you want to use it off camera you will need radio triggers. The Strobist site is a good one for learning to light manually;
http://strobist.blogspot.co.uk/2006/02/welcome-to-strobist.html

check out the Lighting 101 and 102 archives, lower right of page (drop down boxes)

As for filters, yes a UV filter will protect the lens (it doesn't do anything else, with digital) and for reducing light an and filter is necessary - a 4 stop & a 6 stop are a good choice. You can stack them for 10 stops of light reduction.