If you want to try some more advanced stuff this port scanner can be interesting, or else have a look at robtex - the self-styled ‘swiss army knife’ of the Internet. For a good speed test of your Internet connection, try speedtest. To look at how the Internet is connected, try Route Views. Caida provides a lot of tools for Internet routing analysis, as does Wireshark..
site up or down?
isthisdown, this site and this site check if a website is really down or whether it is just your PC/Internet connection
To see what your computer looks like to the rest of the Internet, check out this or this. If you want to know what other websites are on the same IP address, then myipneighbors can tell you.ell you.
