Limera1n was recently released to jailbreak all Apple devices currently on iOS 4.1 (iOS 3.2.2 for iPad), although there are (as always) some bugs in the early versions. limera1n is still working on new bootrom devices, so to be able to jailbreak your iDevice in the future using the same tools (i.e. on iOS 4.2 and newer), you need to save your SHSH blobs. You can follow these 3 steps to save your SHSH blobs of any iOS device.
Step 1: Download the latest version of TinyUmbrella (Windows, Mac, Linux), and make sure that you are running iTunes 10 on your PC or Mac.
Step 2: Launch TinyUmbrella and then connect your iOS device to your MAC or PC. Select ‘Advanced Option’. Your ECID number should already be there, and make sure that the ‘Location’ is set to ‘Cydia’
Step 3: Now just click on ‘Save My SHSH’ and wait for it to complete
Done, now you've saved your iPad, iPhone, or iPod Touch to it's current condition...this will enable you to return your device to the settings it has today. Feel free to try out iOS 4.2 for your iPad in November...this will undo your jailbreak, but you will be able to return to a previous release with your SHSH blobs backed up!
If you have a previous version of iOS, i.e. not iOS 3.2.2. Then you can jailbreak your iPad with an older method. If you have recently purchased your iPad, it will likely have iOS 3.2.2 and you will need to use the GeoHot jailbreak.