Here are my sources of daily crosswords:
http://joseph.king-online.com/client_temps/kol.php
http://webcrosswords.com/daily-crossword-puzzles/ — click Play Now to solve the current puzzle or click the drop down menu (upper right hand, down arrow) for past puzzles.
http://webcrosswords.com/la-times-crossword/ — click on the Featured Puzzle box.
In terms of degree of difficulty – from easiest, I’d say — Thomas Joseph, webcrosswords, USA today then LA Times.
If you hit a rut, try http://crosswordheaven.com/ for hints. Although, webcrosswords, usa today and la times have an option to show the solved puzzle. But that wouldn’t be fun, right?