I just wanted to make a quick follow-up to my original cyrptocurrency post from a few weeks back. This just has a few follow-up links and additional specifics I've come across since that time.
I forgot to mention last week that if you want to participate on the Litecoin or Bitcoin networks and have your own personally managed wallet address (e.g. not a wallet on an external exhange or site, like Cryptsy), then the simplest way to do that is to grab the offical bitcoin-qt client (for BTC) and the official litecoin-qt client (for LTC). These are p2p clients that enable the underlying networks of their respective cryptocurrencies, but they also allow you to create wallet addresses for receiving deposits and making transactions.
If you are particularly concerned about your wallet's security (or are just a very paranoid person :), consider using Armory for your BTC wallet. It pulls data from a locally running bitcoin-qt client under the hood and leaves all of the p2p and networking details to that software. Armory instead focuses on managing your wallet addresses as securely as possible. It has many advanced features such as options for wallet recovery and truly "offline" wallets that can be stored on a computer not connected to the internet at all. These offline wallets require physical access to the machine in order to sign/verify transactions (which you can then send out using a "read-only" online wallet counterpart).
On the mining side of things, Trade My Bit, the multipool I use for mining, has added several new features. Most notable is an automatic exchange that allows you to opt-in to a centralized and managed sale of the multipool mining currencies. Yes, there's a small fee for it, but it means not having to worry about linking up to Cryptsy (or your preferred exchange) for every single currency or having to directly manage a ton of microtrades if you don't want to be bothered with the minutae. You can just get a regular BTC payout from the shared exchange pool at the end of the day. Definitely a very cool feature and the devs there have been very active in updating the pool in general.
If you are using AMD GPU's for your mining efforts, this guide is a detailed step-by-step process for setting up a headless cgminer on Ubuntu. And this optimization guide will help you get the best possible hashrates out of your Radeons.
Lastly, for the AMD crowd using cgminer you are probably aware that 3.7.2 is the final version that supports GPU mining; all further releases of cgminer are dedicated to bitcoin mining on ASIC's and drop GPU mining support. However, someone has taken up the banner and forked cgminer into sgminer. It provides on-going development of and bugfixes for the GPU scrypt mining capabilities in the 3.7 branch of cgminer.