Excel to CSV with UTF8 encoding
I've found OpenOffice's spreadsheet application, Calc, is really good at handling CSV data.
In the "Save As..." dialog, click "Format Options" to get different encodings for CSV. LibreOffice works the same way AFAIK.
A simple workaround is to use Google Spreadsheet. Paste (values only if you have complex formulas) or import the sheet then download CSV. I just tried a few characters and it works rather well.
NOTE: Google Sheets does have limitations when importing. See here.
NOTE: Be careful of sensitive data with Google Sheets.
EDIT: Another alternative - basically they use VB macro or addins to force the save as UTF8. I have not tried any of these solutions but they sound reasonable.
I know this is an old question but I happened to come upon this question while struggling with the same issues as the OP.
Not having found any of the offered solutions a viable option, I set out to discover if there is a way to do this just using Excel.
Fortunately, I have found that the lost character issue only happens (in my case) when saving from xlsx format to csv format. I tried saving the xlsx file to xls first, then to csv. It actually worked.
Please give it a try and see if it works for you. Good luck.
Save the Excel sheet as "Unicode Text (.txt)". The good news is that all the international characters are in UTF16 (note, not in UTF8). However, the new "*.txt" file is TAB delimited, not comma delimited, and therefore is not a true CSV.
(optional) Unless you can use a TAB delimited file for import, use your favorite text editor and replace the TAB characters with commas ",".
Import your *.txt file in the target application. Make sure it can accept UTF16 format.
If UTF-16 has been properly implemented with support for non-BMP code points, that you can convert a UTF-16 file to UTF-8 without losing information. I leave it to you to find your favourite method of doing so.
I use this procedure to import data from Excel to Moodle.