Parafilm
Kevin Kelley's Cool Tools recommends Parafilm for closing bottles. Now that's a name I haven't heard in many years!
That reminds me: I've always wanted to get some useful glassware for the kitchen. A couple of graduated cylinders would be really nice. A set of beakers. And I bet a 250ml Erlenmeyer would be handy for holding juices and sauces. And, yes, a roll of parafilm to seal them all.