Name the many references in different contexts in Halacha to snow?
- Whether a frozen mass of it can constitute the wall part of an eruv demarcation. (Aruch Hashulchan או"ח שסב:טו)
- Purges sins. (See the Gr"a on "לא תירא לביתה משלג".)
- A description of the color-shade of tzara'as.
- Whether it counts as water vis-a-vis a mikva.
That you're not allowed to break it up on Shabbos in order to use the melted water (Shulchan Aruch, Orach Chaim 320:9).
Can it be used to cover blood after Shechitah Can you toivel or your Keilim in a snow drift
Similar: whether you can wash your hands in it (for eating bread, waking up, etc...)
- Does snow invalidate the shach of the sukkah? The Aruch Hashulchan says probably: http://he.wikisource.org/wiki/%D7%A2%D7%A8%D7%95%D7%9A_%D7%94%D7%A9%D7%95%D7%9C%D7%97%D7%9F_%D7%90%D7%95%D7%A8%D7%97_%D7%97%D7%99%D7%99%D7%9D_%D7%AA%D7%A8%D7%9B%D7%98
And from the same section of the Aruch Hashulchan:
Is snow considered to be a roof for the laws of tum'ah?
Snow is not m'kabel tum'ah.
- Whether snow is muktzah.
Not quite Halacha, but the string changing color to white as snow on Yom Kippur to show that atonement for the Klal was successful .
btw: this week yutorah.org has featured this week http://www.yutorah.org/lectures/lecture.cfm/740735/Rabbi_Mordechai_Torczyner/Snowball_Fights_in_Jewish_Law_and_Thought
An important Shiur on all things Having to do with snow a VIdeo Here Chopping on shabbos,salting,Shoveling and snowball fights Here:
Ben Ish Hai S"B Yito 11 permits people to walk on snow on Shabbat. [Also, later on he discusses if you allowed to mush snow into a cup of water to make it cold, and prohibits it (as well as S"A O"H 320- and Alex's answer). ]
Shulhan Aruch (ibid.) prohibits the crushing of ice, however, permits the placing of it in a cup to make things cold (also see for lengthy discussion the aforementioned BI"H and later on in that Parasha).
See also the Mefarshim on that S"A.