Gene & Protein nomenclature: N-Myc, c-Myc, et. al
There is a useful set of links to nomenclature guidelines for all of the main genetic systems at this Wikipedia page. Personally, I think that the Saccharomyces cerevisiae system works best: it manages to cover dominant and recessive alleles of a gene, the name of the protein, how to refer to a related phenotype, and the use of a parallel convention for the designation of ORFs.

Unfortunately there is now no going back - there are many different systems and there is no hope of unifying them. When this plethora of naming conventions is combined with the reluctance of so many scientists to stick to the guidelines, we have a recipe for near anarchy.

Edit - On the specific topic of MYC nomenclature:

The v- and c- prefixes come from the early days of oncogene research. Viral oncogenes such as myc and src were found to be related to (derived from?) similar genes in normal cells. Thus v- means viral and c- means cellular.

This can be seen if you peruse the HUGO entries for the four MYC family members encoded in the human genome (extracts below). They all have an approved name which relates them back to a viral oncogene found in the genome of avian myelocyomatosis virus. This was the founder member of this gene family. Thus c-myc was the first myc-related gene found in the human genome, and is the one that is responsible for Burkitt's lymphoma. It is true, as @Leonardo says, that in tumours the expression of this this myc gene in lymphatic tissue changes due to chromosomal rearrangements, but this is not the origin of the designation c-myc.


  MYC
  Approved Symbol:      MYC
  Approved Name:   v-myc myelocytomatosis viral oncogene homolog (avian)
  Previous Symbols &amp; Names:   "v-myc avian myelocytomatosis viral oncogene homolog"
  Synonyms:   bHLHe39, c-Myc
  Chromosomal Location: 8q24
  
  MYCL1
  Approved Symbol:      MYCL1
  Approved Name:   v-myc myelocytomatosis viral oncogene homolog 1, lung carcinoma derived (avian)
  Previous Symbols &amp; Names:   MYCL, "v-myc avian myelocytomatosis viral oncogene homolog 1, lung carcinoma derived"
  Synonyms:   bHLHe38, "l-myc protein", LMYC, "myc-related gene from lung cancer", "oncogene lmyc"
  Chromosomal Location: 1p34.3
   
  
  MYCL2
  Approved Symbol:      MYCL2
  Approved Name:   v-myc myelocytomatosis viral oncogene homolog 2 (avian)
  Previous Symbols &amp; Names:   "v-myc avian myelocytomatosis viral oncogene homolog 2"
  Synonyms:   bHLHe38
  Chromosomal Location: Xq22-q28
  
  MYCN
  Approved Symbol:      MYCN
  Approved Name:   v-myc myelocytomatosis viral related oncogene, neuroblastoma derived (avian)
  Previous Symbols &amp; Names:   NMYC, "v-myc avian myelocytomatosis viral related oncogene, neuroblastoma derived"
  Synonyms:   bHLHe37, N-myc
  Chromosomal Location: 2p24.3