I'd have to say one of the hacks that I've become rather fond of is the one where you can automatically mount your external ROM, so that if you choose to clean up some of the auto-installed .cabs that you're not fond of, you have that much more space that you can use for other things:
[HKEY_LOCAL_MACHINE\System\StorageManager\AutoLoad\TRUEFFS_DOC1]
"Bootphase"=dword:2
"Order"=dword:1
"LoadFlags"=dword:1
"DriverPath"="Drivers\\BuiltIn\\TrueFFS1"
[HKEY_LOCAL_MACHINE\System\StorageManager\Profiles\TRUEFFS_DOC1]
"MountHidden"=dword:0
"Folder"="Extended_ROM"
"PartitionDriver"=""
"Name"=""
"DefaultFileSystem"="FATFS"
[HKEY_LOCAL_MACHINE\System\StorageManager\AutoLoad\TRUEFFS_DOC1]
"Bootphase"=dword:2
"Order"=dword:1
"LoadFlags"=dword:1
"DriverPath"="Drivers\\BuiltIn\\TrueFFS1"
[HKEY_LOCAL_MACHINE\System\StorageManager\Profiles\TRUEFFS_DOC1]
"MountHidden"=dword:0
"Folder"="Extended_ROM"
"PartitionDriver"=""
"Name"=""
"DefaultFileSystem"="FATFS"