I am a small vendor, is it worthwhile for me to register when the UN is such a large organization?

Yes, of course. UNOG procures on an international basis from vendors of all sizes and from all geographical locations. Sometimes our requirements are large and sometimes our requirements are small. For this reason, we have different levels of registration and companies can choose the level at which they wish to register based on the size of their company and the size of contract that they are able to manage. A description of the different levels of registration and the requirements for each level can be found in Chapter 3.1.3 of the UN Procurement Manual. Guidance on how to complete the additional levels of registrations is available here:  Completing the additional levels of registration | Level 1 and Level 2