SQ, VS, and NZ have offered the "Escapade" RTW, which can be quite cheap compared to other alliance plans. It used to be on the SQ US website, but it's been taken down, so I don't know if it's still available. SQ also has its own RTW program, and probably still has (at least) a two-carrier plan with VS.

United and Emirates also have a very affordable biz class RTW, provided you like DXB.