Originally posted by canyontraveler Actually the Ross Hinged Camera level I asked about in my original post (#2) is a bubble level that fits in the hotshoe. It goes for about $40. The reason I thought maybe the first level (Seculine) might be better is because in a discussion of this problem someone brought up the fact that sometime the camera itself may be slightly off and therefore if you used one of these devices you would need to be able to adust the degree of slant. The Seculine sells for just under $50 I believe.
The hotshoe bubble that soccerjoe showed can be had for as little as $3. Certainly a better price than $40-50. I've got one myself, and it works great for tripod work.