Each bit coin is currently trading at about $120.
I thought it would be interesting to see what my computer could do, and modern CPUs just are too slow to be productive. My reasonably fast video card can only manage to earn me about one cent every 3 hours, meanwhile it's consuming more than that in electricity, so "mining" bitcoins has moved from the realm of typical computers and on to specialized hardware.
There are sites which accept bitcoins for legitimate uses, Wordpress, for instance now accepts them. Bitcoins can be divided into smaller parts, so you can pay in increments smaller than a US penny, even at today's high rates.
It's been in the news a lot due to the rapid rise in speculation, and thus value. Bitcoins that used to be worth pennies are now worth over a hundred dollars.
Mining them is actually not creating new bitcoins. Mining uses computers to do the arduous to of verifying and finalizing a bitcoins transaction. If I send you a single bitcoin, it goes through a significant process to make sure that the transaction is cryptographically secure so you can't take the coin back, or duplicate it in the process.
I order to make sure people have an incentive to perform this work, for every chunk of these transactions you process for the community you are automatically awarded a certain number of bitcoins. This happens according to the code, there's no central authority doing this. These are new, never used bitcoins. Keep in mind that a bitcoin is merely a cryptographic key or signature, so it resides as a chunk of data you now have to store. You typically run a program called a wallet to store these coins/datachunks and release them as you trade with others for goods or services.
But it's a first to the finish line puzzle. Many people might be working on the same chunk, and the first to finish it gets the award, then you have to start all over again with no reward.
Over time, each data chunk gives you fewer and fewer coins. Right now you get 25 coins per chunk, about $3,000. As time goes on, the price will probably go up, but you'll also get fewer coins in return for the same amount of work. Eventually the amount you get for each chunk will be 0, and no more coins will be released. There will never be more than 21 million bitcoins ever produced.
Once they are done, in about 125 years, people will be doing this work based on transaction fees, but by that time I suspect the currency will have collapsed.
Further, by that time computer technology may have advanced enough that we can solve these computationally difficult problems quickly enough that the currency simply won't be secure, even if there's still some interest in it.
Still, a number of other people are starting up a number of other currencies based on the same idea. It requires a peer to peer network of people, but once you reach a critical mass it manages itself.