To learn the basics about reading notes, read this. When you're ready to drill them, read on!

Note Identification Flashcard Drills in Order of Difficulty

My favorite way to use these flashcards is in Challenge Mode. I'd like you to see how many you can get right in the span of 1 minute. Then I want you to try to beat that. Keep re-doing the exercise until you feel smooth and confident, are scoring a high number of right answers (14 or more easily in 1 minute), and have a high success rate.

LEVEL: BEGINNER SIGHT READER

Regardless of how long you have been playing, if reading notes by their letter is new to you, start here.
 

Open Strings

• Flashcards (plain old)
• Practice (requires free account)
• Gamified
• Test

Notes on the D String
(Optional) D String, with helpers, just to practice, here.
(Optional) D String, without helpers, just to practice here.
1. D String Note Identification flashcards. Repeat the 1-minute challenge until you are comfortable reading notes on the D string, are getting at least 14 correct, and have a success rate of at least 80%.  
2. D String Note & Finger Identification flashcards, practice, game, test (some activities require a free account sign-up).

Notes on the A String
(Optional) A String, with helpers, just to practice, here.
(Optional) A String, without helpers, just to practice here.
3. A String Note Identification flashcards. Repeat the 1-minute challenge until you are comfortable reading notes on the D string, are getting at least 14 correct, and have a success rate of at least 80%.  
4. A String Note & Finger Identification flashcards, practice, game, test (some activities require a free account sign-up).
5. D & A Strings combined Note ID flashcards. Repeat until comfortable.
6. D & A Strings combined Note & Finger ID flashcards, practice, game, test.

Notes on the E String
(Optional) With helpers, just to practice, here.
(Optional) Without helpers, just to practice here.
7. E String Note ID flashcards. Repeat until comfortable.
8. E String Note & FInger ID flashcards, practice, game, test
9. A & E Strings combined Note ID flashcards. Repeat until comfortable.
10. D, A & E Strings combined Note ID flashcards.  Repeat until comfortable.

Notes on the G String
(Optional) With helpers, just to practice, here.
(Optional) Without helpers, just to practice here.
11. G String Note ID flashcards.
12. G String Note & FInger ID flashcards, practice, game, test
13. G & D Strings combined Note ID flashcards.
14. G, D & A strings combined Note ID flashcards.
15.  G, D & A strings combined Note & FInger ID flashcards, practice, game, test

All Strings
16. G, D, A & E Strings combined Note ID flaschards here.
17. G, D, A & E Strings combined Note & Finger ID flashcards, practice, game, test

Then, jump to number 11 below.

LEVEL: LATE BEGINNER SIGHT READER

Late Beginners who are familiar with accidentals (sharps, flats and naturals) can now start recognizing notes on the staff with accidentals. The below links are only the Note ID flashcards.

NOTES ON THE G STRING (with accidentals)

18. Practice identifying all notes on the G string here.

NOTES ON THE D STRING (with accidentals)

19. Practice identifying all notes on the D string here.
20. Then practice all notes on the G & D string notes here.

NOTES ON THE A STRING (with accidentals)

21. Practice identifying all notes on the A string here.
22. Then practice all notes on the D & A string notes here.
23. Then practice all notes on the G, D & A string notes here.

NOTES ON THE E STRING (with accidentals)

24. Practice identifying all notes on the E string here.
25. Then practice all notes on the A & E string notes here.
26. Then practice all notes on the D, A & E string notes here.
27. Then practice all notes on the G, D, A & E string notes here.

28. And finally, every chromatic note here.

29. To continue with the next highest notes, jump to #13 below. 

LEVEL: EARLY INTERMEDIATE SIGHT READER

Now, practice reading the correct notes (natural, sharp or flat) in all the possible key signatures you will encounter them in.

Step 1: All notes in Key Signatures up to 4 sharps
Step 2: All notes in Key Signatures up to 7 sharps (advanced)
Step 3: All notes in Key Signatures up to 4 flats
Step 4: All notes in Key Signatures up to 7 flats (advanced)
Step 5: All notes with accidentals with all key signatures (advanced, but not as hard as you'd think!)

LEVEL: INTERMEDIATE SIGHT READER (the HIGH notes)

Once you're comfortable with the notes in 1st position, start practicing identifying notes in the very high range on the E string.  Try to beat your last score every time and you'll get this stuff down in no time!

And yes, I would really recommend practicing them one by one like this! It will be much faster in the end to gradually add on one note, than to suffer through the full gamut of notes and make painfully slow progress. As you practice, you'll decide which notes are landmarks for you, and base the other notes around that note. Then you'll get faster and faster at it!

Start like with the first one, then progress up by one note at a time:
30. Up to high C here. 
31. Up to high D here.
32. Up to high E here. 
33. Up to high F here.
34. Up to high G here.
35. Up to high A here.
36. Up to high B here.

Make Your Own Exercise 

37. You can make adjust the flashcards to your preferences here. 

This is especially helpful if you are a violist! Adjust the settings to match the sequence above! (C, G, D and A strings, obviously!)

Sight Reading

SightReadingFactory.com

Now that you know how to read the notes, it's important to practice sight reading. You can pick up any piece of music and try to play it, beginning with easier songs and exercises. Set a metronome to an easy speed and try to make it through the entire thing (or to a pre-determined stop point) without stopping. Even if you can't get the note in time, keep playing. That is the benefit of practicing sight reading. You must keep going even if you miss a note! In this way, you will get a lot more notes out of your instrument and prepare for a real playing situation!

You can create a free account and get 20 new exercises each day. But you can play each exercise an unlimited amount of times.

One tool that I like to recommend is this new website called Sight Reading Factory. You will have to adjust a lot of settings to get started, so pick the easiest version of everything to begin:

A. String Family, Violin, Level 1, 4/4 Time, D Major, then adjust the Tempo in the exercise to something that seems easy, possibly 40 bpm.
The Tempo is going to be the most important factor here. Look at the hardest part of the music, decide how fast you think you can play that, then set the tempo to that speed. 
If you go too fast, it will all just be a scramble and you'll have a lose.
Have a win, set the tempo to a slower speed.
Then you can speed it up.

B. To make it more challenging, change the key to G Major, then A Major. 
    Change the key signature to include 3/4, 2/4 and 4/4.

C. As you get better, add in more key signatures and more difficult time signatures, and finally, advance the Difficulty Level.