Exporting Activities

You cannot export activities for a group of leads.  However you can create a smart list with the Had Interesting Moment filter and use the Date of Activity, and use the Source, Description and Type constraints to specify those Interesting Moments whose associated leads you want to include in the list.

Thanks Elliott
That gets me a list of the leads rather than the activities themselves (of which there could be multiple for a single lead).
I will continue playing around with the smart list and see what I can come up with.

Cheers
Simon

You can get a bit more granular by creating  separate smart lists for each Interesting Moment and then you can create a Lead Performance report and use these smart lists as custom columns. 

If your leads can have the same Interesting Moment multiple times and need a count of those by creating score type fields for each IM you want to count and setting up a smart campaign to increment the field value by 1 each time it occurs.  Then you can create a view that includes those columns.  If you need the count for specific periods, rather than for all time, you'll have to have fields for each of those periods (week, month, quarter, year) and then reset them to zero at the end of each period.

Not ideal, but something that might be useful.

You could also look at writing something using the SOAP API to pull out activities of a certain type. Depending on how many leads and how far back, it might be a good alternative.

I am going to have to learn the SOAP API ;0)