My pick of the diaper bags is the "Maxpedition Colossus Versipack".  Available here:

http://www.maxpedition.com/store/pc/viewPrd.asp?idproduct=379

Officially, it's designed for carrying firearms.   Also works great for sippy cups, cheerios, changing pad, a few diapers and other essentials.   Don't tell anyone.  :-)

Not too big, not too small.  Available in your choice of manly colors.

I also have mini and jumbo "rolly poly" pouches (http://www.maxpedition.com/store/pc/Pouches-Pockets-c7.htm) clipped on the sides (again, originally designed for weaponry...).   Those make extra space for a picnic or a water bottle and fold up when not needed.

Built better than any other bag you have.   It is truly an awesome dad bag, and won't get mixed up with other diaper bags on the playground :-)

There's some old discussion about it here:

http://www.athomedad.org/node/3200

It actually doesn't move much.    The strap comes off of the bag at an angle that wraps around your body closely, and the back side of the bag is covered with this ventilated mesh material that is somewhat grippy.    If you shove it back around to the side of your back, it stays there fairly well.   If you slide it forward, you can open the bag and get stuff while it's still hanging on your shoulder.    It rides kind of like a messenger bag, but better.   Not quite as stable as a backpack, but better than you'd think...

I have a JEEP bag. Quite manly and black in color. No flowers here. Plenty big, Has elastic straps for two bottles and lots of pockets. Also, a cell phone holder ,Wallet holder and did I mention pockets? Has a changing pad. It's black too. Cheers!

Shannon Carpenter has some really funny and useful tips on making or buying a manly diaper bag at http://daddyshome.org/blog/?p=544

Al Vice-President, Daddyshome, Inc. - The National At-Home Dad Network www.daddyshome.org

You guys are way too nice. If you poop, wear it until you get home.

But for any long or extended trip away from home, having all the diapers, wipes and other baby supplies that you need is essential, and companies like Diaper Dude recognize it.  They have created a line of diaper bags specifically for men, so that they can have the convenience a diaper bag provides while still looking manly.

I have always used a school type backpack with several pockets, the two straps make it easier to carry as well.-Aaron

The best bag I used was the Baby Sherpa backpack, in a handsome blue with black accents. But sometimes I used a photographer's vest my wife got me. It has pockets all over. In winter, after very early on, I just used my heavy winter coat's cavernous pockets. In summer, after the kids are two or so, cargo shorts.

It has only been in recent weeks that I have not had to carry around even a spare pull-up. More than six and a half years of schlepping supplies! I feel almost liberated (even more so next week when my younger one starts preschool).

But I have always tried to travel as light as possible. Diapers, wipes, a snack if I remember, bottles back when I had to. Sunscreen in the summer, of course. Anti-poo goo (hand sanitizer). I wasn't much for table covers, spare clothes or any of the other frills.

As for the Skeletool, yeah, it's a great idea, but, like I said, I like to travel light. I carry a small Swiss Army Knife that is almost as useful. But I do feel naked without it. It's great for trimming straws to the right length, so they don't poke eyes out, and for slicing fruit (I used a credit card a few times to slice and peel apples when my knife was AWOL). And the tweezers are tremendously useful during the early days of drinking from those milk cartons with the collapsible straw that frequently collapses down into the carton itself. Also, with those cartons, I have found it very helpful to poke an air hole into the top, so an accidental squeeze doesn't send milk fountaining into the air.

And a pen. It is a tool, entertainment, and weapon (I always pull it out when passing suspicious dogs — no joke). I cannot remember a time in my adult life when I didn't have a pen on me at all times. I frankly don't understand people who go without one.