Neither is really a cactus. The big plant is either Kalanchoe luciae or Kalanchoe thyrsiflora--they look very similar, you need flowers to tell them apart. Not sure on the last one.
Eric, I am lucky enough to be sitting in th uk with a gentleman who has seen both species of kalanchoes in habitat (madagascar) and in cultivation; he says k thrysifolia. Me, I'm glad to learn a bit.
I'll make things a bit more confusing, maybe. 1) No such thing as Kalanchoe thyrsifolia -- a thyrse is a type of inflorescence, so K. thyrsiflora would be correct, BUT... 2) Kalanchoe thyrsiflora is now recognized as being a synonym of Kalanchoe tetraphylla, so that is the name that should be used.
Both Echeveria and Aeonium are rosette-leaved succulents in the Crassulaceae. Aeonium species are primarily Canary Islands endemics, while Echeveria is a Central American genus. From what I recall (of an admittedly small sample), Echeveria have one to many usually one-sided, axillary, unbranched or sparsely branched inflorescences (cincinni), with 5-merous, fleshy flowers usually in shades of orange or pink, while Aeonium usually have a radially symmetric, terminal paniculate inflorescence (thryrses, I think) (one per rosette) with up-facing 6- to 12-merous, flimsy yellow flowers. Although probably not universal traits, the leaves of Echeveria are thicker, shorter, less fibrous and more boat-shaped. I'm happy to be corrected on the characteristics of these fascinating plants.
