A site with links to virtually every semiconductor datasheet that exists or existed...worthwhile bookmarking...downside: You need to know who made it/them...have a guess, OC71, Mullard, Phillips etc...BC108 - almost everyone!! The same with chips, just go for the usual suspects...
Anything current you should find on the major suppliers sites, RS, Farnell/Element 14 and so on...
https://sdw.lapinoo.net/a.html
For valves/tubes try this...you only need the generic type No. for this, e.g. ECC83, 6AU6 etc..
http://www.tubedata.org/
Steve A.