conntrack.php
A really simple log thing. Tracks how many active connections a server currently has, and averages them, calculates min/max, etc. It gets the number of current connections from /proc/sys/net/netfilter/nf_conntrack_count, if you’re interested.
By default, it samples once each second for a minute. At the end of that minute, it inserts the data into a database. Additionally, if the program detects a tty, it will tell you how many connections there are, once a second.