This is a very open ended question, ya know. Do you want actual useful info or chest beating about how fast guys have gone?
In the last year several people have hit 200mph with lipo batteries, before that there were Nicads or NiMH that hit 225mph.
-Re-propped F5B plane 228mph (24 cells)
-Shubler Vector 225mph (24ish cells)
-Electrified F3D pylon 205mph (12S lipo) video:
http://www.rcgroups.com/forums/showt...38#post5383523
-Electrified Quarter Midget Q40 pylon 201mph (9S lipo) video:
http://www.flyemfast.com/files/BestVen.wmv
-Nemisis F5D 201mph (5S lipo) video:
http://thetick.rchomepage.com/Nemesis%20.wmv
Much of the stuff is commercially available but get ready to fork over some cash. If you are on a budget, 150mph is not hard to attain. What is your skill level and what is your goal??