Rick Steves Convertible Carry-On, Price:$99.00 at Luggage Pros 2500 cu. in.21" x 14" x 9", weighs 3.5 lbs.Converts from suitcase to backpack with comfortable shoulder straps and padded waistbelt. Three exterior pockets. Includes two mesh bags and clip-in security pouch. Internal and external compression straps. Zipper expansion adds 500 cu.in. This is a very small pack, so be prepared to pack super-light.
 

High Sierra Transport, price: $109.99 (31% off retail price) at eBags plus FREE shipping 3564 cu. in. 23" x 14.5" x 8.5", removable daypack 14" x 12" x 5.5", weighs 4 lbs , 8 oz. Large front load main compartment opens for easy packing. Removable shoulder strap with padded shoulder pad on the left side panel. NOTE: Cloth zipper pulls cannot be locked securely. Use luggage lock or cable lock on the metal bases of the zippers.

High Sierra Railpass, price: $139.99 (30% off retail price) at eBags plus FREE shipping 5015 cu. in. 26" x 15" x 9", removable daypack 14" x 12" x 5.5", weighs, 5 lbs, 8 oz. Large front load main compartment hinges open from the side for easy packing. Removable, adjustable aluminum stays can be bent to fit the contours of your back to customize fit and increase comfort. NOTE: Cloth zipper pulls cannot be locked securely. Use luggage lock or cable lock on the metal bases of the zippers.

High Sierra Compass, price: $149.99 (32% off retail price) at eBags plus FREE shipping  5408 cu. in., 29" x 15" x 10", daypack=860 cu. in. weighs 6 lbs, 8 oz. Two large main compartments; the back compartment hinges open fron the side for easy packing. Zippered divider panel between front and back compartments opens to make one large compartment. Removable, adjustable aluminum stays can be bent to fit the contours of your back to customize fit and increase comfort. NOTE: Cloth zipper pulls cannot be locked securely. Use luggage lock or cable lock on the metal bases of the zippers.

Caribee Zulu 75L, price: $169.95 plus FREE shipping at eBags 27" x 16" x 12", weighs 7 lbs. 8 oz.  Detachable daypack. Adjustable Action Back Harness System. Pre contoured aluminum stays promote comfort and back support. Dual zip main compartment with internal divider. Lockable zip housings. 

Thunder Bay 65L, price: $169.95 plus FREE shipping at eBags 26" x 13" x 9, weighs 8 lbs. Detachable 28 L daypack. Side shoulder strap for carrying when backpack straps are tucked away. Advanced Back Harness System. Internal Vertical Aluminum Stays. Dual zip main compartment. Lockable zippers.

Thunder Bay 75, price: $179.95 plus FREE shipping at eBags 28" x 14" x 9", weighs 9 lbs. Detachable 28 L daypack. Side shoulder strap for carrying when backpack straps are tucked away. Advanced Back Harness System. Internal Vertical Aluminum Stays. Internal Vertical Aluminum Stays. Dual zip main compartment. Lockable zippers. External compression system.

Eagle Creek Thrive 65 L, price: $200 at eBags plus FREE shipping 3750 cu. in., 22.75 " x13.5" x 9.5", weighs 5 lbs, 8 oz. Removable daypack. Full front panel load. Zip-away X-ACT suspension. Central Lock Point secures main entry points with a single lock. Detachable Rain Safe cover is waterproof for inclement weather and provides security in crowded areas. Exterior and interior compression straps. Integrates with Pack-It. Modular Daypack: Contoured padded shoulder straps, clipping system, lash points.

 
Osprey Men's Waypoint 60 Pack, price: $229 at Moosejaw plus FREE shipping Medium: Volume cu.in./liters: 3700/60. Weight: 3lbs13ozs/1.73 kgs. Large: Volume cu.in./liters: 3900/63. Waypoint Day Pack Volume cu.in./liters: 600/10 Weight: 1lbs2ozs/0.51kgs. Interchangeable IsoForm harnesses help you customize the fit while a built in ErgoPull hipbelt keeps the load comfortably on your hips without being bulky. A detachable daypack with plastic framesheet keeps your smaller items safe. Large panel zip to allow easy access to main compartment. Zip away straps.  

Osprey Women's Waypoint 60, price $229 at Moosejaw plus FREE shipping  Small: Volume cu.in./liters: 3500/57. Medium: Volume cu.in./liters: 3700/60. Weight: 4lbs4ozs/1.73 kgs. Waypoint Day Pack Volume cu.in./liters: 600/10 Weight: 1lbs2ozs/0.51kgs. Award-winning Ethereal suspension (same as Aether 60) with aluminum headrail for ample headspace Panel load access Detachable daypack Foam sidewalls Women's IsoForm harness and built-in ErgoPull hipbelt.

Eagle Creek W Thrive 75L, price: $230, plus FREE shipping at eBags 3550 cu. in., 28" x 13" x 11", weighs 5 lbs, 14 oz. Removable daypack. Full front panel load. Zip-away X-ACT suspension. Central Lock Point secures main entry points with a single lock. Detachable Rain Safe cover is waterproof for inclement weather and provides security in crowded areas. Exterior and interior compression straps. Integrates with Pack-It. Modular Daypack: Contoured padded shoulder straps, clipping system, lash points.

The North Face Backtrack 50, price:$259, plus FREE shipping at eBags 3051cu. in., 22.75" x 13.75" x 6",  weighs 6 lbs. 7 oz. Ergonomic contoured shoulder harness. Airmesh backpanel. Hipbelt with adjustable cant angle. Zippered suspension cover doubles as a rain cover. Large main pocket with internal gear compression straps and mesh divider .Removable day pack clips into place. Lockable zipper sliders.

Eagle Creek Explorer LT Women's Fit, price: $250 at Luggage Online plus FREE shipping 4200 cu. in., 14" x 22" x 8.5", daypack=1200 cu. in., weighs 4 lbs, 2 oz. Fixed women's suspension accommodates 15"-19" torso lengths. 3-In-1 Travel shell offers rain protection, check through security and acts as a stand alone duffel. New fully adjustable hip belt is fully padded and contoured to accommodate hip circumference up to 50". HDPE Frame Sheet and one curved stay to distribute load weight from back and shoulders.

The North Face Backtrack 70, price: $288.95 at eBags plus FREE shipping  4250 cu. in., 28" x 15" x 7" , weighs 8 lbs. 8 oz. Removable day pack clips into place. Braided cable through top carry handle for lockable security. Zippered suspension cover doubles as a rain cover,  Sleeping bag compartment with wet / dry divider. Large main pocket with internal compression panel with zip mesh pocket.
 

Still don't see the right pack for you? Check out my places to buy backpacks to find the right pack at the right price.

Wheeled Bags:
I don't recommend wheeled packs, but if you feel compelled to buy one, then here are some of the packs available.
 
A.T. Gear Access Carry-On Wheeled Backpack with Removable Daypack, price: $149.99 (24% off retail) at eBags plus FREE shipping 2300 cu. in., 20.5" x 14" x 8", weighs 9 lbs., Removable interior pack measuring 17"x13"x7". Inline skate-style wheels with corner protectors.Hidden padded backpack straps are stored behind the zippered padded back panel. Really small backpack--for extremely light packers only.

Victorinox Trek Pack Plus 3.0 24" Women's Wheeled Backpack, price $139.99 (67% off retail-- CLOSEOUT), at eBags plus FREE shipping 4700 cu. in., 24" x 16" x 11.5", 8 lbs , 14 oz. This wheeled backpack features shoulder straps that are set closer together and have a curvature to naturally fit a woman's shoulders. Front daypack is detachable for use as a stand alone piece.

Still don't see the right pack for you? Check out my places to buy backpacks to find the right pack at the right price. 

Prices listed above are in US$. Price and availability of packs is subject to change (please let me know if the prices have changed or the packs are no longer available and I will correct my listings ASAP).