Covering Array Library
most combinatorial testing problems have varying numbers of values per
variable, in some cases all variables have the same number of values
and a pre-computed array can be found.
A library of pre-computed covering arrays can be found here. The arrays were computed with IPOG-F, a variant of the IPOG algorithm. IPOG and IPOG-F are both available in the ACTS tool, which can be downloaded from this web site. Arrays are available for t=2 to t=5, with 2 to 6 values per variable, and for t=6 with 2 to 5 values per variable.
In many cases the arrays on this site are the smallest known, but newer algorithms may produce better results. Charles Colbourn maintains a collection here of the smallest uniform covering array sizes for up to 20,000 variables for t=2, and up to 10,000 for t=3 through t=6. Note that Colbourn's database records the best known array sizes but does not include the arrays.