Search & replace across all of Wikipedia
Do you need to correct a spelling error throughout all of Wikipedia?
Are there terms you need to linkify wherever they occur?
Do you need to replace a category tag on 500 articles?
AutoWikiBrowser can do that and more. It's a free-licenced semi-automatic editor created by Wikipedians, available to editors who have made at least 500 edits in the main namespace.
System requirement: Internet Explorer
Read more: Wikipedia:AutoWikiBrowser
Lupin's Live Spellcheck