Clerics have the ultimate get out of grapple free: freedom of movement. Wizards have to be more creative. Wizards have a lot more options, but they will generally range from being effective at one part to another.
Heroics: This is a flexible spell but it has limitations. Since the target has to meet all of the prerequisites, Improved Grapple won't work unless the target has Improved Unarmed Strike. Close quarters fighting works best if the target has combat reflexes, but can still be useful even if the target doesn't. However, it helps the fighter avoid a grapple, it won't help a fighter who is already grappled.
Bull's Strength provides a minor bonus but has a lot of other utility. The anti-grapple utility may be enough to make it worthwhile.
Enlarge person is generally superior to bull's strength, however. It adds +5 to the target's grapple check (+4 size, +1 strength) which is useful both for avoiding grapples in the first place and for escaping grapples. Also, what is sometimes more significant, the default monster with improved grab can only use it on creatures that are smaller than it is. There are exceptions, but there are lots of creatures that would grapple a medium fighter that aren't able to improved grab a large fighter.
Grease is a generally useful spell that is helpful for getting out of grapples. Since it has a duration, it could also be cast prior to the fighter being grappled and help him avoid being grappled in the first place.
Gaseous Form also can enable a target to escape a grapple, but as a touch range spell that doesn't move you away, it can be risky to use.
Ray of enfeeblement can make it more difficult for a monster to establish a grapple but unless you somehow managed to get improved precise shot, the 50% chance of hitting either grapple participant makes it a risky manuever once the monster has the fighter.
For helping a target who is grappled escape a grapple, benign transposition and baleful transposition (I've seen wizards carry small white mice to baleful transposition a friend out of a grapple). For less involved tactics, however, Dimension Hop, Dimension Step, and Dimension Door can't be beat. Get the target out of the grapple and get yourself out of attack range too. Dimension Shuffle, Regroup, and any of the other various PHB II movement spells could be useful in this too. Even teleport or teleport without error could be used in a pinch.
)- but Gaseous Form (only 3rd lvl) is effective as well!
