First up - Pentatonics. Where would we be without them? Some people say better off, but I say, nay!
Pentatonics get a bad rap because they are so easy to get under your fingers initially and are the ultimate oh-no-I-am-lost-what-can-I-play-scale so they get played a lot. A lot a lot. So they get called tired, worn out, and cliched. Sure, they can be, but any set of notes can have that happen to them, but for some reason the pentatonics get the brunt of it. No one says the mixolydian scale sounds tired or is over played do they? Okay, well maybe the blues scale gets it's share of abuse too, but pentatonics get it the worst probably.
Pentatonics are as hip as you want to make them be. Jaco used them in every solo he ever did just about and some of his most famous licks (like the unison line from Havona or almost his entire distorto solo on Word of Mouth) are almost all pentatonic. Some other guys named Coltrane, Hancock, and Metheny use them all the time and they sure don't sound cornball when those guys play them. You can play super inside using them, or you can get way spacey Sun Ra outside with them.
The bible on pentatonics for improvisational use is a book by a sax player from Boston named Jerry Bergonzi. He has an entire series of books about improvisation and one completely devoted to just pentatonics. They are not just for sax, they work for any instrument. The books are highly highly recommended if you are looking for material to work on for improvised music.
Bergonzi is big into patterns and recipes, ways of creating re-usable phrases and making lick factories so you don't just get a single lick you get a process and a pattern for making a lot of licks on any kind of chord or with any kind of scale.
His pentatonic book outlines a simple process for creating lines and starts you off with a set of 4 ascending lines and 4 descending lines as an example. Those same lines are in the PDF below converted into bass clef since he only does treble clef in his book. These lines work really well on bass!
There is a lot more in his book than just these patterns. He discusses what pentatonics to play when and how to get outside incrementally if you want by using different pentatonics over different chords. Go check 'em out on the web at http://www.jerrybergonzi.com/books.htm .
Here he is blowing over All The Things You Are and using some of his stuff.
The Pentatonics - download or print. Contains Cmin, Amin, Emin, Dmin, Gmin, and Fmin.