Mabel's Labels has a Limited Edition Camp Combo pack of their sturdy, colorful, waterproof labels for sale until the end of June. It has all the labels you need to identify your kids' clothes, toiletries, backpacks, bags, goggles, cleats, shinguards, hats and more (it would take me all summer to list all the ways you can use these labels!). The Camp Combo is a far better value than their Basic Kit: for $5 more, you get all the labels included in the Basic Kit, plus 10 extra Sticky Labels, 8 extra Tag Mates labels, and the 2 free friendship bracelets. If you order in February (that's today!), you get a $2 discount, so you pay $37.95 instead of $39.95 -- but the combo pack itself is only available till June, so make sure you order yours before then.
Disclosure: I did not receive a sample or monetary compensation for this post. The views and opinions expressed here are my own.