Before Travelin' Junior came along, Travelin' Mom and I had a strict carry-on only policy, making it easy to go standby and bypass luggage lines. Post-TJ, we carry enough gear to outfit a small arctic expedition, forcing us to join all those we formerly mocked in the checked luggage line. Making matters worse, we only have so many hands (TJ isn't doing much heavy lifting at this point) to carry the stroller, car seat, and carry-ons (all while corralling TJ), so we pack for three in one giant suitcase.
Although three in one bag is no problem size-wise, it's a little trickier weight-wise. Thanks to the airlines' 50-pound suitcase weight limit, we routinely play the carnival game of guessing our bag's weight before heading to the airport. Of course, if the guy guessing your weight at the carnival misses, he owes you a cheap stuffed animal. If you guess your suitcase weight wrong, you may be shelling out $50 or more to the airline.
Fortunately, as with most games, this one gets easier over time. I barely even need to do the ol' weigh-yourself-then-hold-your-bag-on-the-scale trick anymore. On a recent return from New York, our bag weighed in at an even 50.0 pounds. It was all our gate agent could do not to applaud.
For those who don't want to deal with the weight-game hassle, or just like any gadget they can find, Ricardo Beverly Hills actually makes a suitcase with a scale in it. 
I'm not sure how popular it is, since I've never seen one in my travels (believe me, I'd notice). I'm also not sure how durable the device would be after a couple of baggage handler beatdowns, but it's an interesting idea.
Should you eschew the suitcase scale route, keep in mind that some begging may get you an essential extra pound. We had our bag packed to weighty perfection on our return from Austin, Texas last week when my friend dropping us at the airport handed me the 800-page book I had loaned him last year. Since I really did want the book back, I toted it along and hoped for the best. Our bag originally weighed in at 49.5. When I placed the book on top of the bag, the scale hit 51. The AA gate agent must've seen my dejected look, because she said we were close enough and let me throw the book in the suitcase. My shoulders and neck cannot thank her enough.
There's of course one obvious alternative. Just pack less. I guess I need to retrain myself on packing light. Fortunately, there's a good primer website available.
