Useful for any web designer who wants an idea for something new to learn...
 
Server/Other: .htaccess, Cookies.
Namespace: DSD, DTD, NRL, RelaxNG, SGML, W3C-XMLSchema.
Markup: HTML (MHTML), XML (Modularization, WML, XML, XHTML).
Syndication: Atom, OPML, RSS (GeoRSS, MRSS), XBEL.
MetaData: META (APML, DCMI, META, OWL, P3P, PICS, RDF, SIOC, XLink), MicroFormats (Bookmarklet, FavIcon, FOAF, hSlice, MF, POSH, S5, XFN).
Style: CSS (DSSSL, JSSS), XSL (XSLT).
Format-Data: DOAC, DOAP, DocBook, EventsML, GPX, GraphML, MathML, MusicXML, NewsML, OpenMath, PAD, SportsML, XMLTV, XSPF.
Format-Interface: GladeXML, MXML, UIML, XForms, XUL, ZUML.
Format-Site: OpenSearch, OpenService Accelarators, Robots.txt, SitemapXML.
Format-PostScript: EPS, FlashPaper, JDF, OpenXML, PDF, XPS.
Format-Audio: PLS, SISR, SRGS, SSML, VoiceXML.
Format-Vector: 3DMLW, Canvas, Flash, GML, Java (Java3D, XJ3D), KML, POV-RAY, Shockwave, SMIL, SVG, UML, VML, VRML, WireFusion, X3D, XGMML.
Database: ADO, Apache Derby, CSV, DB2, Firebird, ODBC, Oracle, SQL (MSSQL, mySQL, PostgreSQL, SQLite), SVN, XML (Container).
Behaviour-Client: JS (AJAX, DHTML, DOM, E4X, ECMAScript, IE-Expressions), VBS (VBScript).
Behaviour-Server: CFN (Coldfusion), JS (JSP, SSJS), Lasso, MSASP (ASP, ASP.NET), Perl (CGI), PHP, Regex, SSI, XML (XInclude, XPath, XQuery).
Rich-Internet Apps: ActiveX (HTA), Air (ActionScript, Flex), Curl, Java (J2EE, JavaFX, JVM), Silverlight (WPF).
Cloud Widget Apps: Adobe Air, Google Gears, Mozilla Prism, Titanium.
Web-Apps: .NET (C#, C++, J#, VB.NET, XAML), OpenLaszlo, Python (Iron), Ruby (Rails), SmallTalk (Seaside, Squeak).

Very well done Alex

Great work, Alexander

Nice list Alex.