squid has a log file access.log (unless u changed it) which shows you every connection through it. you can install and configure squidARG for the later part. basically it takes the squid logs as input and shows you a detailed report of all transactions including the highest cache hits, user history, the most visited sites etc etc.
i basically do a
anytime i want to see who is going where. i also have the squidARG but its set to generate a daily report. so at runtime i just use the tail thing.