I recently purchased a Carson Lens Pen LP99 from B&H PhotoVideo. What a fantastic device. Simple to use and very effective for cleaning finger prints, smudges and grime from your filters and lenses. I highly recommend this tool - about $10. Don't buy the mini - that one is for small optics. The lens pen uses a non-liquid compound for cleaning the lens after first brushing off dust and other debris with an attached natural hair brush.
The Lens Pen device is NOT for cleaning your sensor. I have my eye on a sensor cleaning device that i'll review in a few weeks.
Here's a little UTube video from Carson Optics