There are a number of different ways in which you can help the open source community or a particular project/person.
Helping the community
LinuxFund - They are actively funding the OSS community, providing development grants of upto two thousand dollars
Linux International - Provides grants to Linux projects
Software in the Public Interest, Inc. - Orginally set-up to help fund Debian GNU/Linux it now also provides grants to a limit set of projects.
You should also remember that a number of big name brand companies jumped on the Linux band wagon and maybe receptive to requests for support ( IBM, SUN, SGI, Oracle, Sybase, Intel )
Helping a project/person
Hopefully the project/person has set-up a webpage detailing ways in which you can help, financially or otherwise. Typically the page should contain links to popular wishlists ( such as ThinkGeek or Amazon ) and/or electronic payment services ( such as PayPal ).
So, setup a webpage with multiple ways for people to show you support [ See Getting Project/Person Support below ]
If you are looking for actual financial funding, why ? You should always have a strong valid reason why you are asking for financial support from the open source community - otherwise your unlikely to get it!
It could be you need certain equipment, books or membership to a standards body, but don't expect to make a full time living out it! If you are certain you have a valid request for funding then look at the section Helping the community above. It would also be a good idea to have a ThankYou page ( similar to the FSF's ThankGNU's ) listing those who have contributed, and perhaps more importantly showing what has been done with the contributions!
ThinkGeek Wishlist - Obvious choice for all geeks :)
Amazon Wishlist - The most popular form of providing support and/or showing your apprieciation it would seem
Cafepress - Set-up some project specific mechandise
PayPal - More direct form of financial support
NoChex - Similar to PayPal, but in the UK
