Ultralingua Grammatica Spelling and Grammar Checker - German is a great application that comes with sophisticated error recognition and extensive suggestions.

Grammar checking
Detection of subtle problems in grammar, syntax, punctuation

500,000+ forms
Includes conjugated verb forms, slang, and even technical language.

Launch with a click
Use a single keystroke to activate Grammatica from within other applications.

Verb conjugation
Conjugate verbs in every tense!

Expandable and Customizable
Add other language modules -- even add your own entries!

Here are some key features of "Ultralingua Grammatica Spelling and Grammar Checker - German":

· Ergonomic interface
· Tight integration with Microsoft Word (among others)
· Multilingual interface
· Old and new spellings

Limitations:

· 10 days trial