pearCalc is a freeware calculator, application-launcher and text replacement tool that uses incredibly little space on your screen. As calculator it provides a broad range of operations (i.e. +, -, *, /, sin, cos, tan, log, %, mod, ^, sqrt ...). Of course it also handles parenthesis correctly.
The application-launcher function lets you launch applications simply by entering an application name. pearCalc can also launch web pages with your favorite browser and generate new emails with your favorite email-app. Furthermore, pearCalc can also be used as a text replacement tool in all text editors that support services.
There are some interesting things about pearCalc:
It uses almost no space on the screen, because it just provides a textfield for expression-input and result-display, no unnecessary buttons and stuff like that. If it still uses to much of your valuable screen real estate you can simply hide and reactivate it via a global hot key.
If you place pearCalc in your Applications-Folder it also provides its pearCalc-service to all Cocoa-based applications via the Services-Menu. So you can calculate expressions or launch applications even within Mail, TextEdit or any other Cocoa-based app.
You can define a list of shortcuts which enable easy currency-conversion or you can just use these shortcuts as constants. Of course you can also define shortcuts for application-launching. You can even set the order in which these constants should be processed simply via drag&drop. These shortcuts can also be used for text replacement purposes in service-enabled texteditors.
BTW: If you're in the mood for nice quotations from famous people like Einstein or Edison, pearCalc can give you some too.
pearCalc supports multiple languages, currently included are English and German.