Script Summary: Easily switch Wikipedia language version with a heading link (see the screenshot). Retrieves links to other Wikipedia language versions (user-specified) for given article (if present), and places them beside main article heading on the top of the page. Can be both used as translator and quick link feature.
Version: 2013.07.22 (0.3.3)
Compatibility
Tested in Firefox 21 (Greasemonkey) / Chrome 26 (Tampermonkey) / Opera 12.
Screenshot

Description
+ Shows headings in user-specified languages beside the original heading (if the article in that language exist).
+ Those headings are clickable links to the other language versions.
+ Shows links only to the language versions you want.
+ Will be launched also when you visit other, non-favorite language version.
+ Language code is Wikipedia's address for given language (xx.wikipedia.org -> code is 'xx').
Feel free to report any issues (remember to provide exact URLs where it doesn't work as supposed) here or on GitHub: https://github.com/jakub-g/greasemonkey-userscr...
Version history
v.0.1 (10.08.2010):+ initial version working on Wikipedia
v.0.2 (30.03.2011):
+ language indicator (es, en, ru...) presented beside the link (useful for links that have same URLs in different languages, like surnames, company names
+ works on other Wiki pages: Wiktionary, Wikiversity, Wikisource, Wikibooks, Wikiquote, Wikinews
v.0.3 (09.10.2011):
+ support for HTTPS Wiki versions, including secure.wikimedia.org
+ code rewritten to be more comprehensible
v.0.3.1 (20.10.2012):
+ updated GreaseMonkey meta, whitespace changes
v.0.3.2 (23.05.2013):
+ fixing non-standard XPath expression. Works in Firefox, Chrome, Opera now.
v.0.3.3 (22.07.2013):
+ fixed the issue after Wikipedia code change: links to current lang were displayed
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Renamed from "Wikilinks: Interwiki Heading-links To Chosen Languages" to "Wiki language switcher" 14.07.2012 (the previous one was obviously too long;)