I am surprised that adultery is not criminal offense prosecutable by law in India or elsewhere. Adultery is ground for divorce in civil courts and for settlement of marriage property, yet there is no recourse under law for punishment under adultery. If it were to be so, then also, divorce will necessarily follow since it's impractical that couple continue to live together after one successfully sues another for adultery. Yet, spouse in question will have to suffer imprisonment before venturing out for new marriage or life of singleton. If couple reconcile after extra-marital affair then victim needn't sue his/her spouse, but s/he should have option to do so.
Why am I proposing a draconian view on a matter which not necessarily follows from criminal intent? I admit that some causes of adultery are possibly worth sympathizing (viz. neglect/violence by other spouse). However, said spouse has right to seek divorce and then pursue other love interest. If cause is simply love outside of wedlock then also existing relationship should be terminated before entering into new one. Adultery hurts its victim (other spouse) mentally and emotionally, and is detriment to children too, if any, and there should be recourse under law to persecute the offending party. Absence of such laws is cause of so many hate-generated violence where victim of adultery takes law into his/her hand to punish offending spouse and often involved third party. This should specially be so in developed societies where marriage is contract of free will and while I espouse the right of each to enter and exit the contract of own volition, violation of terms while in contract should incur penalty by state.
Edit 22/09/2008: Follow discussion in comments for better explanation.
Edit 19/12/2008: In light of new information (thanks SS) about existing law on adultery (IPC 497) I would like to clarify few things. I somehow feel that despite civil violation of contract there should be imprisonment and not merely penalty. I am not very clear about differences in Civil or Criminal law so if Civil law permits that, "civil law" should replace "criminal law" in above post. Existing law also seems very vague and incomplete and charges third party and not the offending spouse which was my main point.