Back Pack for Digital SLR and lenses

I was out the other day hicking w/ my Cannon digital SLR and ONE telephoto lense, wish I had the wide angle, and got to thinking that it would be nice to have a back pack to hold the camera and two or three lenses. That way it wouldn't have to be strung over my shoulder.
The back pack should be small enough to go in a saddle bag along with the rest of my gear as it will be going on a trip with me out West after the MOA rally, and possibley to the top of the Rockies rally two weeks after (a two week trip out west).
Just looking for any advice on what others might be using and where to look.

Thanks and happy New Year!

I use the Tamrac zoom 19. Its a holster and good for a 10"(?) lens. My 20/500 is shoe horned in with body off. I also have a 18/200 that's no problem w body on.

I wear it on my chest when "flower sniffin" for fast access without dismount.

I also have a Tamrac adventure backpack that can carry a monopod.

I like the Tamrac system because you can carry a pouches for lens, P&S cam, water bottle, etc. on the outside, easily accessable.

BTW, the holster was bungeed to the outside of my travel bag and survived high speeds for long periods.

Got this one from Santa

Their website

Perfect for photojournalists, the SlingShot 200 AW uses a unique sling design to go from "carry mode" to "ready mode" in just seconds. Carried comfortably on the back, it easily rotates to the front so you can get to your camera quickly. The SlingShot 200 AW holds an SLR with mid-range zoom lens attached 3-4 extra lenses, cables and accessories and has a full access lid to make loading it a snap. This feature-rich bag also includes a built-in memory card pouch, micro fiber LCD cloth and two generous organizer pockets. It's certain to surprise even the most demanding photojournalists.