One good thing to have in mind is that when one is minimally serious about data structures, then on covering the topic of hash tables, it is a quite good chance to talk about the "birthday paradox". In the analogy, each day would correspond to a slot in the hash table and each person would correspond to an item to be inserted into the table.
If one takes this into account, the analysis of collisions is meaninful from a probabilistic point of view, which matters a lot.
Changing the subject a little, in a replacement that lasted, say, 15 minutes (tops), the cable modem is back again working, which means that playing with tunneling under Linux (especially, using the IPSec interface) is back again a possibility.
Oh, and it seems that Ubuntu's dapper is "mom proof". Well, at least, she has been learning to use it with some hiccups, but, then, personal computers aren't things with which she plays everyday. She was surprised to know about Wikipedia and its broad coverage. And, indeed, it is superb.