Some stuff I've made.
Get instant email notifications of transactions, and confirmations of transactions, on any Bitcoin address.
Web based utility for checking DNS records for a hostname or IP address from a set of more than 80,000 public nameservers. Query up to 100 servers at a time, optionally filtering by country.
Convert hexadecimal byte values to and from human words using the PGP word list. This can be useful for verifying PGP, GPG, OTR, SSL (or other cryptographic) fingerprints read aloud.
I maintain Planet SysAdmin, an aggregator of System Administration related blogs.