Finance::Quote is a Perl module which can fetch on-line stock quotes, including those from American, European, Canadian and Australian markets. Information from a number of investment houses is also available. Features include currency lookups and conversions, automatic failover support, and loadable user modules.
mptc is a Perl script to help you work out whether you're on the cheapest mobile phone network/tariff for your phoning habits. You feed it an itemised phone bill and tariff pricing information, and it will tell you how much that bill would have cost on different tariffs. So far it only supports UK network pricing systems, but could easily be extended and applied in other countries.