Texture packs

[The Unbeholden]

The newest

http://www.moddb.com/mods/half-life-ultra-definition-model-pack
http://www.moddb.com/mods/half-life-overhaul-pack
http://www.moddb.com/mods/half-life-gold (though the multiplayer part is still unfinished)
http://www.moddb.com/mods/ultimate-pack

Note worthy mentions

http://www.moddb.com/mods/diamond-half-life-final

Unreleased

http://www.moddb.com/mods/hlquiver
http://www.moddb.com/mods/half-life-redux-v2 (v2 was released last year but it's still very unfinished)
http://www.moddb.com/mods/half-life-enhanced1 (by the hl improvement team)