A great resource for these kits is
Minimus.biz -
mini/travel size nirvana. And you can buy all kinds of things individually that you'd normally have to buy in packs: condiment packets, various snacks, towelettes of any kind you could want, mini OTC medicine, etc.
Some of my favorites:
"Emergency" cold pack - $1.93
And by emergency, I mean, it's summer in the south outside.
Mini spray sunscreen - $3.79
Evian mini spray - $8.24 (good lord - if you know someone going to France, have them stock up on these for you. I just got a 5 ounce one of these in the Paris airport for 4 euros)
Antiperspirant wipes - $0.31! They also have a ton of different mini deo sticks.