These are great for travel as there are no pieces that separate to become lost and each takes very little space (borderline pocketable).
1) Turnstile: "The Turnstile puzzle consists of two overlapping circular disks. Each disk has 12 pieces, 6 are triangular ('corners'), 6 rectangular ('edges') alternating along the rim of the disk around a hexagonal centre. The pieces have curved sides. The disks have three pieces in common, two corners and one edge, so there are altogether 10 corners and 11 edges. Each disk can be rotated. A rotation should be a multiple of 60 degrees since only then can the other disk move again."
2) Port to Port: "The main area consists of a 2x7 rectangle and this can be moved one tile to the left or to the right (i.e. there are 3 positions; left, right and center). There are also two small plungers which each hold a 3x2 rectangle of tiles, 4 of which are common to the main area. These plungers are connected so that if one is pushed upwards, the other is pushed downwards and vice versa. Three of its tiles form a ship, and the aim is to move them from one side of the puzzle to the other."
3) Top Spin: "consists of 20 numbered round pieces in one long looped track. You can slide all the pieces of the loop along. There is also a turntable in the loop which can rotate any four adjacent pieces so that they will be in reverse order. This in effect swaps two adjacent pieces and the two pieces on either side of them. The aim is of course to place the pieces in numerical order."