Craps is all about the odds, and the 6 and 8 are decent bets, because only the 7 is rolled more frequently. A bet on that giant 6 and 8 pays even money (betR$5, and if a 6 or 8 is rolled, you winR$5), and your bet stays up until a shooter sevens out. (That never happens! Actual results may vary.)
The best craps bet in terms of odds is the Don't Pass/Don't Come bet, which give a lower house an edge. You can also take advantage of the free odds betting option, which you can use after making a Pass/Don't Pass bet or a Come/Don't Come bet and has no house edge.