That depends a lot on what kind of simulations you want to run, as many packages are optimized for different uses. I find LAMMPS quite nice, but it has so many features that it can be overwhelming, especially if you want to do something out of the ordinary for which tutorials can be hard to find.

I started out using DL_POLY (https://www.ccp5.ac.uk/DL_POLY_C) and found it a pleasant place to learn MD. It's a powerful software package, but with a small footprint and not too many features out of the box which makes it relatively easy to grasp.

You may try Desmond (https://www.deshawresearch.com/downloads/download_desmond.cgi/). It comes with Schrodinger Maestro interface. It's very user friendly and they also provide one click analysis.

OpenMM is very flexible.

Thank you all for helping.

This question is too old but I'll answer in case it would be helpful for someone.

It depends on what you want to achieve.

For example; In which specific domain you're or will be applying MD such as; in physics, material science (particles, theoretical etc) or biological science (proteins, nucleic acids, membranes etc).

When someone say user friendly, believe me I've never seen a more beautiful, fast and high quality simulation illustration or graphs generated by DESMOND.

Even, If you're a newbie, you can prepare and simulate a system step by step using your mouse only i.e everything is GUI based in DESMOND. However unfortunately, It's a highly expensive tool to pay for.

But You can still download and use it for free with an academic id, provide to Dr. D. E. Shaw.

https://www.deshawresearch.com/downloads/download_desmond.cgi/

And on other hand AMBER is also user friendly, Just in case if you're little bit good in reading the script or commands and other tutorials provided by AMBER community on his web page.

But again You've to pay for AMBER i.e 100USD for academic 1-year subscription.

There's is another GROMACS: http://www.gromacs.org/

It's also easy to install and use. I suggest Justin Lemkul tutorials.

http://www.mdtutorials.com/gmx/

And above all if you're looking for free, easy, not hectic (not to install it in your PC) etc. Then I recommend MDWeb (Molecular dynamics on web)

http://mmb.irbbarcelona.org/MDWeb//main.php

And I'm not sure about how much nano second simulations you can do or achieve in their online server. But I've heard about 20ns, may be you can do more (I don't know) but still that's pretty good for a small protein or peptide.