The first one is mammillaria vetula ssp gracilis
The second is Brasiliopuntia brasiliensis
The third one is a Rhipsalis... But I can never get a confirmed ID on it... I have one too and have it labeled as rhipsalis cereuscula... but could be R. cassutha. I've even seen pictures that look like it labeled as R. baccifera or R. viraga!
Maybe you can get a better ID from here.
the last one is an Echinopsis of some type that needs more light. Probably E. oxygona but could be Echinopsis eyriesii.... I can't tell the difference.

#4 Thanksgiving Cactus, Christmas Cactus, Easter Cactus -- you find out for sure which when it blooms (fall, winter, or spring) as they all look the same in terms of foliage.

Hey Fizgig,

"#4 Thanksgiving Cactus, Christmas Cactus, Easter Cactus -- you find out for sure which when it blooms (fall, winter, or spring) as they all look the same in terms of foliage."

FYI: The foliage DOESN'T all look alike. The Thanksgiving have sharp, angled joints, the Christmas have rounded joints, the Easter just a sort of rounded segment or leaf w/out joints or angles.

There's an exceptional link (if you search for 'holiday cactus) that shows the difference in foliage w/ some lovely line drawings as well as pix. They also have somewhat different flowers.

The time of year of the blooming is not the determinant at all & is often manipulated by the nurseries who sell these to us. The bloom of the Easter Cacuts is completely different than that of the other 2 in shape & form.

My recent Thanksgiving cactus actually bloomed at New Years' w/in a day or 3.