I've always wondered, how exactly do you practice scales? I don't think it's possible. Most people would say playing the scale is practicing a scale, but how does that help? I'd rather use picking excersises, preferably making backstrokes while I ascend and descend in a mode... Thats a good way to memorize any scale for instance...

A Phrygian 1 b2 b3 4 5 b6 b7

------------------------------------------------------------|
------------------------------------------------------------|
------------------------------------------------------------|
---------------------------------5------5-7---5-7-8-5-7-8-|
-------5------5-7---5-7-8-5-7-8---7-8------8--------------|
5-6-8----6-8------8----------------------------------------|

--------------------------------------------5-----5-6---5-6-8|
-----------------5------5-6----5-6-8-5-6-8---6-8-----8------|
5-----5-7---5-7----5-7------7--------------------------------|
--7-8-----8---------------------------------------------------|
--------------------------------------------------------------|
--------------------------------------------------------------|

Then do the same thing decsending.

This ones a little weird, but I heard someone in this forum mentioned this mode earler, and it is featured in alot of Rock, (Nirvana, Zepplin etc.)

Also check out pentatonics, start to improvise with that, but branch out too.

Also get more well aquainted with the positions of the note on the fretboard,
Joe Satriani suggests that a player should map out where all the Cs are, all the Gs , Es, etc. Try setting up a metronome and doing that, then it becomes easier to locate scales and move across the fretboard.

This takes a LONG time but when it finally comes it's awesome.

www.musictheory.net
www.ultimate-guitar.com/lessons/

Ultimate Guitar columns are useless, everyone on that site is pretty ignorant and biased, but the lessons done by the UG staff are pretty good, and they have a scales and soloing section I think you'd like.

P.S. sorry for the information overload, bad habits :D