I'm in the process of applying for admission to a PhD program this Fall after several years in industry. Due to the late timing of the application I'm looking at self-funding my first year, but after that I would rather not be doing so. What would my options be for funding after the first year beyond just TA and RA-ships?
In the US, various funding agencies (NSF, NIH, DOE, ...) have fellowships you can apply to for predoctoral students. They tend to be very competitive compared to internal sources (Teaching Assistantships, Research Assistantships, Graduate Assistantships), but they may offer a higher stipend.
Depending on your field, professional societies also offer fellowships: American heart association, Whitaker foundation, Gates foundation.
Industry also offers some in association with various schools: Siemens, Raytheon, Johnson & Johnson.