LaTeX is the solution to all the headaches you ever had using M\$ Word, OpenOffice Writer, ... etc especially when it comes to larger documents like books or scientific work. LaTeX documents look the same, independent of the system they are rendered on (theoretically. but this is more a "this web page should look the same in firefox 1 and firefox 2" - theoretically, NOT a "this page looks the same in IE and Firefox"-theoretically... ;-) ). This is part 1 of my LaTeX blog series, I start with the basics you need to follow the rest of the posts - the LaTeX environment for your OS and taste. here are my suggestions:
• Mac OS X:
• LaTeX Distribution: MacTex
• Editor: TexShop

TexShop is included in the MacTex distribution, it's a very nice editor with a big "do it now" button.

• Linux:
• LaTeX Distribution: Texlive
• Editor: whichever you like...

Use VI, Emacs melts your brain and kills your pets.

• Windows:
• LaTeX Distribution: MikTex
• Editor: TexNicCenter

The directory you have to set on installation of TexNicCenter is <program files>\miktex\miktex\bin, or wherever you installed MikTex...

there are many more environments available, so if something doesn't suit you, keep looking for a better distribution, i haven't seen them all ;-) Installation instructions can be found on the pages linked above, except for texlive on linux; that should be part of your linux distribution's package manager (if it's not, you should switch *g*). in ubuntu "apt-get install texlive" should do the trick. if you want to test-drive your shiny, new latex installation, you can pick a sample from The Tex Showcases for testing.