One of the trickiest things we do as musicians is sight read a new piece of music. We must first have a command of the basics (visit the MUSIC READING SKILL BUILDING TAB). Then we can apply that knowledge to any new piece of music. But there never seems to be enough material to practice and it's hard to find just the right level of piece to help you grow. Much like Baby Bear, it's either too easy or too hard and never juuuuuuuust right!
These two sites provide a wealth of material for study and practice. Since they are written exercises, you will need to give yourself a good starting pitch. (You can grab one off of the keyboard on Musictheory.net or your phone.) Remember, when you are using solfege syllables, you can set your "Do" at any place in your vocal register that is comfortable. Look to see how high and how low you must go in the exercise and practice away!
The other tricky thing is being able to hear something and recognize what you heard. Whether it's an interval, a melody, a rhythm, or a chord, your ability to identify what you hear is one of your most powerful skills as a musician.
In addition to all of the great practice exercises for reading music, Musictheory.net also has a section for ear training. Once again, you can set the parameters so you are practicing at just YOUR level.