Perseus under PhiloLogic Reference Collection

For most purposes, these separate databases for the reference works should now be obsolete. You can consult all these resources together in Logeion, which contains copies of the dictionaries that are more frequently updated, and more besides: the DGE and DuCange accompany LSJ and Lewis & Short, and you will also find frequency data, collocations, and examples from the corpus. There is even an app for your phone! The dictionaries below are useful if instead of searching for particular entries (the normal mode of using a dictionary), you want to search the full text. 

Greek Dictionaries

• This collection, and in particular Liddell & Scott, saw extensive editing in the Spring of 2009. For an idea of what 'correcting data entry errors' means, look up παρασκευάζω or Ἀθήνηθεν in your other online dictionaries. Please report further infelicities!
  
• Liddell and Scott's Greek-English Lexicon (1940)
  
• Liddell and Scott's Intermediate Greek Lexicon (1889)
  
• Autenrieth's Homeric Dictionary (1891)
  
• Slater's Lexicon to Pindar (1969)
  

Latin Dictionaries

• The Latin dictionaries have seen some light editing as well. Headwords in Lewis & Short have been regularized to spellings with -i- rather than -j-, as was already the case in the Elementary Dictionary. -v- has been maintained throughout. Clusters such as adf-/aff-, adl-/all- are now aligned between the two dictionaries. Please report further infelicities!
  
• Lewis and Short's Latin-English Lexicon (1879)
  
• Lewis's Elementary Latin Dictionary (1890)
  

Reference

• the Perseus Encyclopedia
  
• Harper's Dictionary of Classical Antiquities
  
• Princeton Encyclopedia of Classical Sites
  
• Smith's Dictionary of Greek and Roman Antiquities
  
• Smith's Dictionary of Greek and Roman Geography