The easiest way to do this is to configure an input format that can use the flash node input filter. Then you create a flash node to hold the flash content, and then you can create a block that uses a flash node macro to bring the content across. You can use the macro to resize the content to suit the site layout.

If you don't want the flash content to be viewable as a node in its own right simply set the status of the "parent" or "placeholder" node to unpublished. You can still refer to the node from the macro, but you can't view it.

For details of the flash node input filter refer to this handbook page.

An alternative option is the node as block module, although last time I tried to use this there was a bug that prevented flash node from working.