my try:

My friend whats going on
arkadaþým ne haber.
or
arkadaþým naber.
or
arkadaþým iþler nasýl gidiyor.

Here it seems better to say "Arkadaþým, neler oluyor?"

has (name) gone crazy?
name hâlâ çýldýrmadý mý?
name çýldýrdý mý?

He never comes on msn anymore.
Artýk msn´e hiç gelmiyor.

The last time I spoke to him was a few weeks ago.
onunla en son birkaç hafta önce görüþmüþtüm.

I text him to say I was sending him some Christmas gifts
Ona noel hediyeleri göndereceðimi gönderiyor olduðumu yazmýþtým.

he rang me to give me his address information.
Bana adresini söylemek için telefon etti. (Bana adres bilgilerini vermek için telefon etti.)
 
He sent me a few text messages that same day.
ayný gün bana birkaç metin mesajý gönderdi.

I text him on Bayram and I told him to call you.
Bayramda ona yazmýþtým ve ona( no need to repeat "ona"again) seni aramasýný söylemiþtim.


I told him not to forget about the people who care about him the most.
Ona kendisini en çok önemseyen insanlarý unutmamasýný söyledim.

Since then I have heard nothing.
O zamandan beri ondan haber alamadým.

Why is he ignoring you ?
Niye seni görmezden geliyor?

"Arkadaþým, neler oluyor?" is correct but seems like a serious question "what is happening here"
"whats going on" looks like "how are you"

Normally would be OK, but here, s/he is asking what is going on about something, so it is better to use "neler oluyor?"

"name çýldýrdý mý?" is literally correct but i prefer in daily life "name hâlâ çýldýrmadý mý?" meaning "hasnt name gone crazy yet"

I completely disagree with this one. S/he thinks that "name" has gone crazy, you cannot say "name hala çýldýrmadý mý?"! It sounds like something that you were waiting until it happens, "oh, isn´t he crazy yet?". That must be "name çýldýrdý mý?" and even better "name çýldýrmýþ mý?".

Ona noel hediyeleri gönderiyor olduðumu yazmýþtým.
he/she planned to send some gift in the past and we dont know he/she sent it or not.
we´d better use "göndereceðimi"
"gönderiyor olduðumu" means that it is more certain that he/she sent the gifts.

Yes, because it was written "i was sending gifts", not "i was going to send"

Bayramda ona yazmýþtým ve ona ( no need to repeat "ona"again) seni aramasýný söylemiþtim.
you are right but it may be used in long sentences to understand easly i think.

It maybe used, mine was just to show more proper usage.