It seems that if you can add a module to your iGoogle homepage, there’ is a decent chance that you can add that module as a gadget to a Google Wave.
Go to “Add stuff” from iGoogle and browse to a gadget you like. After selecting the gadget, click “share this gadget” and then click “copy and paste a link to this gadget”.

After switching to Google Wave, create a new Wave and then click “add gadget by URL”. Paste the URL, and trim everything out except the string that starts with http:// and ends in *.xml.

You may have to further configure the wave, but with any luck, it should work. It also appears that have temporarily lost the option to add gadgets by URL in subsequent Waves.
YMMV. And no, I don’t have any invites.
Tags: Google, homepage, module, personalization, wave