My guess is ->
on the internet.
You're not mentioning which WM you're using or anything...currently, I'm using KDE, which can be made an orgy in transparency (easily set through menus/the control center). Some apps (i.e., XChat) have own transparency options. As for wallpapers, you might want to check out
DeviantART, for example. If you're using KDE or GNOME, you also might want to take a look at
KDE-look.org and
art.gnome.org, although the latter has been a bit sleepy lately. Qui quaerit invenit.
Where can i get those cool transparent window themes
