Just yesterday my "new" hardware was delivered, a Promise Ultra133 TX2. I think you can buy this piece of hardware since 2004 and I got it very cheap :-) I just installed it for testing purposes and I connected a old 80GB IDE HD. ESXi did recognize the Promise IDE controller and the attached hard drive and I could add the 80GB HD as datastore3.
If I need more cheap space in the future, I have now the option to add up to 4 IDE drives.
Thanks to vm-help.com and their list of supported hardware :-)