I don't mean to offend anyone who is Muslim, so please don't take any of this the wrong way, but I want to know if Islam is a violent religion? I have plenty of Muslim friends who say that it's not but I have skimmed through the Quran and have seen a lot of things that would suggest that it is violent. For example:

Oh ye who believe! Murder those of the disbelievers and let them find harshness in you. (Repentance: 123)

I don't know, but to me that looks like it says to kill anyone who does not believe in what the Quran teaches. Now, I'm not a Muslim nor do I study it. So before I jump to any conclusion I would like to ask a Muslim exactly what that means. Maybe I'm reading it wrong or something. But to me, it seems like it says to kill people who do not believe as a Muslim does. Can anyone (Muslim) explain this please so that I may understand.

If you read through the Bible it can look like a violent religion.
The way I figure it, it is sort of like trying to say being a Pentecostal is the same as being a Catholic. They both use the Christian name but both have very different beliefs.

No Islam into itself is not a violent religion. The bible would have as many if not more references to killing or other issues,

It is the sect and how they teach to practice their faith, Remember in Iraq it is a Islamic government that we are fighting for and with, as it is in many nations there.

Just as we have some groups that call thierself Christian that are scary with guns in camps in Montanta, there are dangerous groups using the name of Religion for their own goals.

I don't hope so islamic is so violent if we read through the holy quran instead of the latest versions which might be modified by some,, it always tells us to be in PATIENCE and the main theme or the allah likes and wishes his followers to be patience unless until any valid reason this itself shows that how allah is merciful,how kind he is... there are some misbehaviours who doesn't obey him,nor thy don't get panic for the DOOMSDAY OR RESURRECTION day... bcoz of some misbehaviours you might took it in the wrong sense

Tafsir Ibn Kathir - Quran Tafsir - The Command to fight Those Who fight Muslims and killing Them wherever They are found
This is the right explanation for this ayat, the fighting is to be fought against those who fight muslims, in self defence. That does not make Islam violent.

As Lavanya mentioned, patience is a strong theme in the Quran, where believers of Islam are asked to be patient in times of good & bad. To show mercy to others,humans & all other living beings.

For example, I am a muslim, a follower of Islam, I try to follow the commands of Allah as much as I can.
I have non muslim friends,had non muslim neighbours, but I have never ever harmed them in anyway for any reason. For one thing because we have to co-exist with them as they have not declared war on us or expelled us from our cities by force,which is one reason muslims can fight a war against anyone.

And my whole family are muslims, never seen them harm anyone and they have very close friends from around the world,many non muslim friends among them.

Thanks to everyone for the answers. And special thanks to firmbeliever, as you are a Muslim. You have cleared this up for me. Now I understand. Thank you.