Tools

Dictionary and language in context
http://www.linguee.co.uk/
Linguee is a bilingual dictionary + a linguistic corpus

Spell checks
http://ludwig.guru/
Ludwig is a smart translator and linguistic search engine

Machine translation
http://www.elanlanguages.com/en/free-translation
Machine translation tool

Language learning
http://learn.lindsaydoeslanguages.com/
very useful and affordable online language courses

Linguistic research
http://www.webcorp.org.uk/live/guide.jsp
World Wide Web as a corpus

Linguistics communites
http://linguistlist.org/indexfd.cfm

Terminology resources