• Chrysothamnus nauseosus ssp. hololeucus (Gray) Hall & Clements, Rubber Rabbitbrush: Bulbs roasted and the juice used as a substitute for glue in attaching feathers to arrows.
• Chlorogalum sp., Soap Root: Bulbs made into glue and used to fasten sinew on the backs of the sinew-backed bows
  
• Grindelia integrifoliavdr. macrophylla (Greene) Cronq., Sticky sap used like glue
• these are some plants which secrete glue .

Sundews are carnivorous plants that use sticky secretions to trap insects to eat, like the unfortunate fly in this photo. They live in swampy soils with poor nutrient content, so digesting and obtaining nutrients from bugs is helpful. (image source)

I don't think humans use sundew glue for anything, though.