Macro Lens for Nikon D3000 for beginners like me?

Guys, can you recommend any macro lens for Nikon D3000, for a beginner like me?

Sigma 50mm f2.8. Won't autofocus on your camera, but then most macro is done using manual focus anyway.

Don't believe it. Some people gush about the joys of manual focusing. You can select the manual setting on your present kit lens and see how much you love it. After that experiment you will probably want the Micro Nikkor 60mm AF-S, Micro Nikkor 85mm AF-S VR, or the Micro Nikkor 105mm AF-S VR. Those can autofocus with your D3000. The 105mm is more expensive. The 85mm is a DX lens that will not work with a full frame camera (which you don't have), reducing weight and cost.
Depth of field is very shallow at macro distances, and at longer focal lengths it gets even shallower. The shorter focal lengths can be good for plants for that reason. Longer focal lengths are favored for insects because of the longer working distance.

Recommend Tamron AF 18-270mm f/3.5-6.3 Di II VC LD Aspherical IF Macro Zoom Lens.
I tried every lens worth trying on my Nikon D5000 looking for a single lens for multi-purpose use. If you are a real wedding photographer or genuine professional photographer you will not be using this lens or a Nikon D-series camera anyway. But for the 90% of Nikon owners who use their cameras on vacation, family shots, and amateur shooting for fun… This is an outstanding lens!

Sigma is a less expensive lens because it is cheaply made and the picture results are less than satisfying. Nikon lenses are good, but for the best bang for your buck you can't beat this Tamron lens.

I was an Air Force photographer for several years and then a wedding photographer until I grew weary of whining controlling mothers of the brides. Photographer is just for fun now so I bought the D5000 Nikon for traveling and wanted a single lens because there's nothing more frustrating than lugging around a camera bag with 2 or 3 lenses when hiking around on vacation.

All the "cons" listed in the other reviews are not very much different than what you will find with the Nikon lenses and certainly worse on the Sigma. If you want to go cheap and don't care about photo quality, then go Sigma. If you are a name brand kind of person, buy the more expensive Nikon, but if you want great photos from one lens at a decent price… You can't beat this Tamron… And with a 6 year warranty no less!

Tamron's 90, tokina's 100 or sigma's 105mm. Alternative, nikon's 85mm f3.5

Try Nikon 105mm f/2.8G ED-IF AF-S VR Micro-Nikkor Lens
I got this lens a few weeks ago, and have used it lightly around the house. It takes amazing pictures! I took some pictures of my wife, just playing around with it, and the pictures are right up there with all all my other pro lenses. I mostly got this lens for wedding photography for close ups on details. I haven't had the chance to use it yet in that arena but look forward to it! The only thing that I do not like about it, is that I'm using this on a DX camera which puts the actual range at 157.5mm. The 60mm macro might have been a better choice for my camera. I'm still giving this lens a 5 star review because of is sharpness and superior quality. If you are thinking about adding this lens to your gear, I highly recommend it!