Submission of papers to ArXiv or similar Apologies for posting such a similar question in a relatively short space of time, but I have a paper that I would like to submit to arXiv.org, whilst it is in the process of being reviewed (which I realise can take a very long time).
However, the submission guidelines say that it must be endorsed by someone currently affiliated with ArXiv. I have heard that it is possible to publish on  vixra.org, but that it is not really advisable. Is there a viable alternative? Or is there a way to contact someone who might be interested in endorsing publication on ArXiv?
Also, I don't know whether it is common practice (or even permitted) to submit to multiple journals.

Don't submit to multiple journals; they explicitly forbid it.  Pick the best one for your paper and wait for the decision; if you're rejected, then you can pick another.
If you are in any way affiliated with a university, you can certainly request that a professor there endorse you.  How did you come to do the research in the paper?  If you worked entirely on your own, it nonetheless benefits you to send a copy to a few people of repute who can comment on it; in fact, an important part of establishing the trust of the community (with respect to the validity and importance of your results) is having a few names in the acknowledgments that demonstrate that you've gotten at least some people interested.  You can ask one of those people for an endorsement.
