Miscellaneous Characters

[Kiyotsuki]

I was just just reviewing a lesson by rewriting phrases using both kanji and kana (as opposed to just kana) and I came across this phrase: ごかげつまえ.
My initial guess was: 五か月前, but... what was that か doing there?
So I typed it up on here, and it came out: 五ヶ月前, and the translation came out accurate "5 months ago." And this time... what's the ヶ doing there?

So, here's my point. What does this character mean, and when/how would one use it?
Also, how are miscellaneous Japanese characters classified? And what other misc characters should I look out for?

[Ewok85]

When counting lengths of time in months its ikagetsu, nikagetsu and the little katakana 'ke' represents that.

Another one of the top of my head is 々, dont know its reading but used to 'double' works, tokidoki, iroiro etc
時々
色々

[Elizabeth]

It is also used as a counter to represent the number of places....三ヵ所 or 三ヶ所.
Sankasho. 　　

[Glenn]

It is an abbreviation of the inanimate counter 箇 (か). It comes from the left half of the top part of the kanji. In simplified Chinese it is written as 个. When written in full size it is better to write か, because of the sound correlation, and also to keep from confusing people with the katakana ケ.