I have never been able to find an application to take calendar files exported as .csv from Outlook and import them into iCal. Similarly, I haven't found anything that handles moving tab-delimited data from Excel into iCal. If such programs does exist and I've failed to find them, then I've given myself work for no reason -- so please let me down gently!
I've written a primitive AppleScript called iCalTextImport to fill this gap. The script works for me, and may be of some use to others. It uses the Satimage osax and Prog_Bar 0.2, both of which are freeware and which are included in the package (acknowledgement is given in the ReadMe). Feedback welcome!
[robg adds: I tried to add a link for Prog_Bar, which is from Spork Software, but their website seems to have vanished and the program hasn't been updated in about a year. I haven't tested this script...]
Mac OS X Hints
http://hints.macworld.com/article.php?story=20050914132515989