Wcalc is a very capable calculator. It has standard functions (sin, asin, and sinh for example), many pre-defined constants (pi, e, c, etc.), support for using variables, a command history, hex/octal/binary input and output, unit conversions, bit-shifting, embedded comments, and an expandable expression entry field. It evaluates expressions using the standard order of operations.
extract_url.pl is a Perl script that extracts URLs from either correctly-encoded MIME email messages or from plain text. It can be used either as a pre-parser for a URL selector (such as urlview), or as a standalone URL selector. It is very configurable, can handle URLs that have been broken over several lines in format=flowed delsp=yes email messages, and eliminates duplicate URLs. It was designed primarily for use with Mutt, but can be used by for any similar purpose. The idea is that if you want to access a URL in an email, you pipe the email to a URL extractor (like this one), which then lets you select a URL to view in some third program (such as Firefox).