(NOTE: This is for flying. Road trips and train trips are entire 'nother animal.)

Weather:
I can easily handle a 50 degree range (and even more if I will only be outside for a few minutes moving from car to door etc.) with my standard array of clothing:

• a pair of Khakis/jeans
• a pair of black pants
• several long sleeve quick dry shirts (or short sleeve if in summer/warmer climates)
• a light merino wool sweater
• a breathable jacket (the same one I wear on the trail)
• a scarf (pashmina or the like)
• walking shoes

For trips like Green Bay, I allow myself a couple of fun things. This trip I have snow pants (though not totally necessary) and some silly hats to wear.

Function:
If I am going to be going to a play or out to a fancy dinner, I tend to pack a nice shirt and a pair of shoes that don't look like I walk 20 miles a week in them and wear my black pants. Its as good as you are going to get with me.
Cope.

I end up packing about the same amount of clothes for a weekend that I do for a week or more. I don't know why, but it seems to work well for me. I think its because I can have a choice in what I wear and my inner 2 year old is appeased by that.

Also on the default list is:

• yoga pants (can work as jammies, workout wear, warmer weather pants as well as being just plain comfy.)
• 2 quick dry t shirts (workout clothes, layers, on their own, jammies etc.)

Tools:
This is where I spend most of my time thinking about a packing list: the gadgety stuff.

• Phone+foldup keyboard+USB charging cable – I have a Palm Centro with the old Palm folding keyboard covers most of my text based needs (email, blogging, writing articles/books (thank you WordSmith!), Twitter, Facebook, banking, misc browsing) and some basic HTML provided I have a web interface I can work in instead of relying on FTP.My phone also has a nationwide plan and is GSM so if I am out of the country I can buy a prepaid card and swap SIM chips.
• Camera+charger+multiple cards (I have a small digital that works for everyday photos and video. If I am going somewhere for more than a week, I will most likely bring my digital SLR for some really good shots.)
• iPod – model varies based on trip length and availability of wifi and or power outlets.
• Solio This can charge my iPod (The nano version can be charged multiple times without draining the Solio and still have power for my phone) I have limited luck with charging it in the sun since I am in airports and in cloudy locations. But when I do road trips, it works really well on the dashboard, hiking has a limited charge time as we are mostly in the trees but it has a charging option so I mostly use it as a spare battery.
• Belkin Mini Surge with USB – For charging everything in my pack. It is brilliant.Go get one NOW.
• Card reader+Cards+Portable Apps – You can use any PC without leaving any of your data on it… and they have Skype in P.A. form now! I also put PDF (password protected) scans of my drivers license, my passport and other emergency information and standard files I use a lot.
• USB rechargable speakers I found these a while back. I like them because they sound great, are chargable via mini-USB, and are tiny (they were originally made to go with some Cingular phone that matched its form factor). I don't think they make them anymore, but I love them.
• optional: if I am on call at work then I take my netbook, an Acer Aspire One which has my full set of tools on it.
• optional: if I will be on a flight longer than 2 hours or if I am visiting my family (i'm a night owl and they aren't), I bring my eReader

Then there's the standard stuff I have in my purse/backpack at all times: notebook, pens, aspirin, etc. Survival gear.
There are also some new toys that I am pondering but that will have to be another post… as will the perfect (mythical) travel tool.