Yeah, I don't recommend buying dedicated rigs, too expensive, and not good for anything except for mining. If you already have AMD cards from the HD 5000 to the HD 7000 line, they will generate at a pretty decent rate (one HD 7970 alone might generate you 1 bitcoin per month), and you just get better power consumption with the latest cards.
You'll generate the least amount with your CPU and an okay amount with Nvidia cards.
The cheapest way is to just use your work computer to generate bitcoins (since your company is paying the electric bills, and it's most likely their computer), but don't expect to generate much that way.
To get money from it is to setup an account at Mt. Gox's BitCoin Exchange, send your BitCoin there when you want to sell it, and have it go to a Dwolla account, and then transfer the money to your bank account. That's the most common and least expensive way with fees.
I guess I'll write an in-depth guide when I get some time in a couple of weeks if there's interest for it. It's pretty simple, took all of 15 minutes for me to setup. I use GUIMiner for mining, setup an account at BitcoinCZ to mine at Slush's Pool, created workers (i.e. computer1, computer2, etc.) and then enter your worker username and password in GUIMiner at the computer you're mining with and then start mining (so that worker gets credit to your BitcoinCZ account). I personally use Bitcoin Wallet to handle my BitCoins (I don't recommend an online wallet, if they go down, your bitcoins do, too), When you want to receive bitcoins, you generate an address, and for BitcoinCZ, you can then put that address down to automatically receive your confirmed bitcoin rewards.
I use Twitter to get hourly updates on prices of Bitcoins from @bitcoinprice, which usually shows the price at Mt. Gox.
I also use this Bitcoin Calculator, which saves your information in the URL.
Here's my estimate going by this current rate at $86 per Bitcoin: http://tpbitcalc.app...tmentperiod=355
As you can see, it's barely worth it. It costs me $26.30 in power to generate a single Bitcoin. If I wait until it goes back up to $265 per Bitcoin (the highest it's ever been), then that's $239 profit in one week: http://tpbitcalc.app...tmentperiod=355
At any rate, Bitcoins might be nothing to like $.04 again, or it might end up being a lot again (up to $265). If Bitcoins end up less than $26.30 (the cost it takes for me to generate one in electric costs), then I might buy a few and just wait until another spike happens. If the price of power is high where you live, it may not be worth it to generate one.