Basic negotiation skills

Here you can find the handouts with some basic negotiation skills.

Signposting and survival tactics

Here you can find a four-page document with exercises on signposting and some survival tactics, which could come in handy during a negotiation. (Source: Presenting in English by Mark Powell)

BBC on negotiations and meetings

Here you can have access to the BBC website on negotiations, where they have useful expressions and/or phrases contextualized in short dialogues available as audio streams with transcripts.

Here you can have access to the BBC website, where they provide some examples for interruptions contextualized in a short dialogue available as an audio stream with a transcript.

Here you can have access to the BBC website, where they provide some examples for agreements and disagreements contextualized in a short dialogue available as an audio stream with a transcript.

Opinions, agreeing and disagreeing

Here you can find some phrases which can be used to express your opinions, agreements and disagreements along with some exercises.

'Like' vs. 'as'

Here you can find the document and exercises on the use of 'like and 'as' along with the key.

False friends for French

Here you can find a list of false between French and English.

American vs. British English

Here you can find a list of the main differences between American and British English. (Source: English Grammar in Use: Intermediate by Raymond Murphy)

Make, do, get and have

Here you can find some information and exercises on the use of the verbs 'make', 'do', 'get' and 'have'.

Emphatic structures and inversion

I am hereby making Unit 34 on emphatic structures available. 

Describing trends

Here you can find a document on describing trends with exercises.

Figures, abbreviations, symbols and currencies

Here you can find some information on writing figures, abbreviations and symbols from the "Interinstitutional Style Guide". You can also find more information on the same topic on pages 24-25 of the English Style Guide used at the Commission.
Here you can find information on writing monetary units from the Guide.

Latin terms, phrases, abbreviations and acronyms

You can find a list of Latin terms, phrases abbreviations and acronyms that can be used in English here.

PS: The abbreviation for the Latin phrase et alii is 'et al.' with a dot at the end.  Here is a general rule for the use of the dot in abbreviations:  If the last letter of the word being abbreviated is not the same as the last letter of the abbreviation, you need the dot.  What are the abbreviations for 'professor', 'doctor', 'mister' and 'abbreviation'?

Mandatory, obligatory and compulsory

These words can indeed be used as synonyms in most contexts.  I also like the first response in the forum at the following link:
http://answers.yahoo.com/question/index?qid=20080507075259AAR2USG

Here is a link for another forum which can be useful, as well:
http://english.stackexchange.com/questions/2902/mandatory-obligatory-compulsory

Commonly confused words

Here is the list of the commonly confused words.

Journalistic titles

Here you can find a brief explanation on journalistic titles used in, e.g., newspaper headlines.  We, however, should not use this style for our titles in administrative writing.  How would you change the headlines provided as examples in the hot-linked document into administrative style titles?

Gender neutrality

"English Style Guide" released by the Commission is hereby available.  On pages 47 - 48 you can find the section on gender neutrality.  

Here you can find the document released by the European Parliament.