1. Integer and Nonlinear Optimization in R - The project "Integer and Nonlinear Optimization in R (RINO)" provides the packages Rbonmin, Rlago (both interfaces to MINP solvers) and solnp.
3. limSolve - Functions to solve linear inverse models (lim), i.e. find the minimum/maximum of a linear or quadratic function subject to equality and inequality constraints, functions to randomly sample lims.