Which parts of your site would the migration script need to handle:
User Accounts
Permissions
Application Data:
* News Articles
* Calendar Events
* Photo Galleries
* Links / Downloads
I can recommend the following modules:
News Article Management: News 1.3
Calendar: piCal or extcal
Gallery: the XOOPS embedded version of gallery is not the latest version, you could try using it, or myAlbum-p
Links: MyLinks (core module)
Downloads: WF-Downloads or MyDownloads (core module)
Just as an aside, what particular issues are you having with Geeklog? Was there any feature (or features) that you are looking for in XOOPS?