MultiBootUSB can assemble multiple live Linux distributions on an USB disk. It presents a boot menu, and works non-destructively on flash disks, can even uninstall distributions again. It furthermore works cross-platform, and can create Linux USB boot disks from Windows.
GParted is a hard disk partitioning application commonly used from LiveCDs. It allows to created and modify partitions, label, check, copy and move, or resize common filesystems. GParted works on legacy MBR bootsectors or GUID partition tables (GPT). Supported filesystems include ext2/3/4, btrfs, f2fs, FAT16/32, hfs/hfs+, lvm2, NTFS, reiserfs/4, ufs, and xfs.
rEFInd is an EFI boot manager (forked from rEFIt), that autodiscovers installed boot loaders, and presents a startup GUI. It supports EFI 1.x and 2.x, PC and MAC systems, has a text fallback, can control the boot order and searching schemes, handles Secure Boot, or start available EFI (BIOS) utilities, and understands most BSD/Linux partition types.