Since a long time, some fans of HL1 work on a convertion of the game with Source engine, This mod is not ready yet but it will be release in 2009 just look this video :
https://www.youtube.com/watch?v=oGlhgVz5r6E&eurl=http%3A%2F%2Fwww%2Ehalflifefusion%2Efr%2Fcommentaire%2Ephp%3Fid%5Fsection%3Dnews%26id%5Felement%3D2306&feature=player_embedded
Amazing !
https://www.youtube.com/watch?v=oGlhgVz5r6E&eurl=http%3A%2F%2Fwww%2Ehalflifefusion%2Efr%2Fcommentaire%2Ephp%3Fid%5Fsection%3Dnews%26id%5Felement%3D2306&feature=player_embedded
Amazing !