When the word ends in -щина what does it mean?

Note:
it-ogo and Larusja provided great explanations. Here are my observations on the question. Perhaps, we could turn it into a community wiki (there is a feature for this) and create the combined answer.

The suffix -щина (or -овщина) is used to form nouns. There are two types of words ending in -щина:

1- The first group includes simple words where the -щина suffix has no particular meaning. There might have been a special meaning in the past but it's now lost and the suffix is just a part of the word as a whole. Some of the words in this group are:

• женщина (woman)
• община (community)
• годовщина (anniversary)
• морщина (wrinkle)
• толщина (thickness)
• трещина (a crack)

2- The second group includes words influenced by history, literature, culture and traditions. Most of such words express criticism and carry a negative connotation. The words in this group can be formed from the names of people, historical phenomena, and notions that are being criticized. When you look at English translations of such words, you will notice that -щина is translated with the help of English suffixes like -ian, -ism, -ness, -dom, -ing and others.

• толстовщина (The Tolstoyan movement)
• обломовщина (Oblomovism; Oblomov is a character of Goncharov's novel)
• маниловщина (Manilovism; Manilov is a character from Gogol's Dead Souls)
• лысенковщина (Lysenkoism)
• чертовщина (devilry, devildom, diablerie)
• поножовщина (knife fight, knifing)
• любительщина (amateurism)
• дедовщина (hazing)
• казёнщина (red tape)
• безотцовщина (fatherlessness, fatherless child)
• обыдёнщина (commonness, uneventfulness, trivial round)
• деревенщина (country bumpkin, redneck; literally, someone from a village)