This plugin for permutation tests applied to GLM was greatly inspired by the Randomise program built in FSL, improving some of its aspects. Here's a comparison of the features:

Feature	FSL Randomise	BV Randomise Plugin
Input formats	NIFTI.	VMP.
Univariate statistics	t and F.	t, F, G
Spatial statistics	Cluster extent, cluster mass, TFCE. All of these can be volume-based (voxelwise).	TFCE, cluster mass. All of these can be volume-based (voxelwise).
Regression and permutation strategies	Freedman–Lane.	Freedman–Lane.
Shuffling possibilities	Permutations or sign-flippings.	Permutations, sign-flippings, and permutations with sign-flippings.
Block permutation	Either whole-block or within-block.	Whole-block and/or within-block, either in isolation or in arbitrary combinations, with multiple and complex levels of tree-like dependence between observations.
Variance groups	One. Cannot be changed.	Two. All maps belonging to the same variance group when using statistic T and F and one computed automatically from the tree when using G statistic.
FWER correction	Within each contrast only.	Within each contrast only.
FDR correction	Yes, separate command. Correction within each contrast only.	(Scheduled) Yes, separate command. Correction within each contrast only.
Overall performance	Generally a bit slower, except for spatial statistics.	Generally a bit faster, except for spatial statistics, that can be extremely slow.
Parallel processing	Yes, with a separate script (randomise_parallel).	Yes, built-in.
Language	Written in C++.	Written in C++.