I'll stray from birds and bugs for a post - and this post may be a mental stretch for the conventional civilian, but bear with me!
So you're going to be on the road/in the air for ~10 days. Pack one bag. Wait, you're a birder? Pack two! Actually, pack one bag that two bags fit into. No, seriously. A small, rolling duffel that counts as carry-on luggage, a backpack with laptop inside, and you're good to go. That third bag is because I didn't much feel like pockets all day, every day (and packed a soft, cloth purse... gasp!)
* Purses for the womenfolk are handy when they fit binoculars, so as not to look horribly awkward in restaurants ;-)
Sample of versatile luggage: the enduring rolly-duffel, the weekendable backpack. Two weeks, or two months, those are my two luggage friends.
Matt and I were lucky because the condo had a very friendly washer and dryer, else I'd have packed a little differently, or just smelled much, much worse. I digress. So 2 pairs of shorts, swimmies, minimal "foundation garments" (read: underwear. Also, bras if you must), 1 tank top, 2 shirts, a lightweight neutral button-down shirt, a hoodie and a sarong. Gentlemen, your packing needs may differ. Pack socks according to shoes. I flopped most of the time, hiked one day, had 2 pr of socks - and they were handy for packing fragile gifts for the return trip! Hiking boots also provided refuge for small items.
Backpack contained laptop and hoodie, along with a few zip-lock bags of camera & phone chargers, not to mention the folded cloth purse. Wallet, sun glasses, chapstick and TSA's mandatory bag of mini-shampoo & conditioner & toothpaste was also in the backpack.
But, Heidi, what about deodorant?! Indeed. My last trip to FL was in 2006 with an automotive testing company that resulted in nearly melting my flops on asphalt - and the drive to/from the airport caused my super-awesome Tom's of Maine unscented deodorant to melt in the trunk. Sadness. Deodorant stones are brilliant, but they do work best with a bit of scruff. So ladyfolk, don't maul your arm pits for about 2 weeks before you leave. Menfolk, leave your shaving stuff at home, too. Unless you need to appear smooth-faced while traveling, in which case facial scruff might not be the best idea. If you've got hair, a comb is probably a good idea, and a bandana is handy for all occasions, take two if you have hair and need to blow your nose.
Anyway, back to the bag-in-a-bag-in-a-bag part - my small, rolling duffel was the one bag I took to Europe last spring, for a total of 14 days on the road (a few days in St. Louis beforehand, a 22 hr layover in Newark, you get the idea). My backpack actually contained everything, with a pile of bird guides to make up for the weight that would have been laptop, had it tagged along. Backpack was tucked into the duffel and for that trip I had an awesome travel jacket with enough pockets that a purse wasn't really required. The weather was such that jeans and long-sleeved things were required and the packing recipe still worked! Binoculars were accompanied by walking shoes, since hiking boots were overkill for visiting the grandmother.
Switzerland, 2008 - for a weekend trip, the backpack was deployed and the duffel stayed with the grandmother.
So what's the moral of this post? Know thyself, and pack accordingly. Or be a hippie while you travel and use the excuse to pack light =)
Or, you can always pay to check your luggage and then have it lost or damaged...