EcoBrew Refillable K-cup for Keurig today. You can get one for just $9.61 (over 40% off), or you can buy them in multi-packs (so you can alternate them out). There's even a nice little gift set that comes with coffee, to get you started, for just $15.
If you have a Keurig, you definitely need one of these. If you know someone with a Keurig, this a a great gift, as it allows you to use any coffee you desire in your Keurig and saves you a ton of money.