Hashing:

hashCode - write your own to comply with a .equals method.
concepts of linear probing, chaining, load factors, when hashing perform 
poorly

BSTs:

insertion, deletion (diagrams, not code)

AVL trees:

calculating balance factors, insertion, deletion (diagrams, not code)

Splay trees:

splaying (say from a find), insertion
            
Quick sort:

runtime, partitioning

trees: general understanding of pros/cons re: data, space, time
sorts: general understanding of pros/cons re: data, space, time