Sometimes my network is going really slow so I dont know if it is my computer, the network or a couple of my friends accessing my NAS.
Chances are it's the LAN network, check other search gigabit / linkstation speed threads here for more info.
Kill all unneeded services on LS, eg bittorrent, media server, print, afp, web access, the 1st two really slow file transfers down.
monitor who is connected to my Linkstation,
Displaying a list of currently logged in users (and possibly the protocols they currently connect to the LS with) should be simple for the LS to display in web admin - you would need to submit a feature request.
how much network bandwidth/traffic it is using
My 2wire 2700 router, it has a small java real-time up/downstream throughput applet I launch via the router GUI, nothing fancy, just current incoming & outgoing throughput, in a graph. Linksys may have one too, the manual didn't say. Feature request to linksys to improve their router if not.
what the the activitity is,
Possible but difficult
Activity: For external access, assuming every program connects to the LS via its protocols' default port eg port 21 for FTP then you could tell what protocol was in use & current IP address connected to it, by enabling logging on the router. If your external users have static IPs lol. Check your manual.
what they are doing / Would there be something that I could put on my Linksys WRT310N router to monitor outside network traffic and use and stuff then?
Again not easy
Technical & a bit OTT for your problem as a PC would have to sit between your router & modem. Try googling ethereal & wireshark.
HTH