How can I forward SMS via Jabber (XMPP) to read them on a PC?
GTalkSMS (Google Project Page) does what you want (and much more).

Edit: After actively developing GTalkSMS, I decided that it's time to spawn a new project called MAXS. See my second answer.

Note: According to the FAQ I have to disclose that I am involved into GtalkSMS. GTalkSMS is an open source GPL licensed Android app. Everyone can contribute.