There are three main groups that make up the market for cryptocurrencies. The most well known is the group that includes Bitcoin, Litecoin and Ether. The second largest group is that of the newer coins, particularly Litecoin and Ripple. Then we have the new coin group, which is made up of Namecoin, Megacoin and Dogecoin. Most people will recognize Namecoin by its association with BitNames. This was a project that offered to have Namecoin integrated into the BitNames platform in order to provide anonymous internet based address registration. However BitNames cancelled this offer, citing security concerns as the main reason.
Namecoin had also looked at giving merchants the option of paying out dividends in Namecoins. This would have been much like what many of the new coins have done. However we saw this project failed due to development problems within the Namecoin code.
The last major group is those that are not associated with any of the other above. These are called side chains and they give additional security to any cryptocurrency because they serve as a backup. As more coins are mined, the amount of security will become more secure. The reason that this is done is that it provides a currency that can act as a reserve to protect the currency. So, if there is a big theft or if the value of the currency drops due to a governmental fiat event the currency can act as a source of backup.