pberg3571, I've always used indoor antennas for scanning. I've tried many duck, whip, and mobile antennas. I've had the best luck with the radio shack 800mhz antenna, but you lose out on 150/460 mhz. 2m half wave whip antennas are the best on 2m and do a decent job with 460mhz as well, and good on local 800mhz, but not so good on distant 800mhz signals. I've had no luck with mobile antennas since I could never get a decent ground plane.
Recently, though, I tried a log periodic beam antenna. I purchased the antenna for a different purpose, but it has now become my main scanner antenna. You can read my post here:
I am near one corner of the building here and I have the antenna pointed towards the direction where my reception was weakest with my other antennas...towards the opposite corner of the building.