I can't help you find your up votes, but since down voting costs reputation, you can find those votes are still active (ie, not those on deleted posts) by looking at your reputation changes - this obviously only works for yourself, you cannot see this information for other users.
The first option is your reputation audit page (as in
http://stackoverflow.com/reputation or which site you wish to check). Then, just use your browser to search for the text
(-1). You then you have the post ID you need, with which you can try and hunt it down manually, this requires effort, so I'd recommend using the audit helper user script as well, which changes the post IDs in to links, saving you valuable time.
Here's an example, a shot of the first of my down votes that happens to still be active:
Without the script (the normal view):
With the script (clickable links):
The second option is to look at the reputation tab on your user profile as this displays downvotes as well:
Unfortunately, you have to expand each individual day manually to search for the down votes, so this is probably quite a bit slower , but as an advantage the posts are linked for you without the need of a user script - and is probably very speedy if you want to find a post you just down voted.
As a final reminder, remember that these methods will not find down votes against deleted posts.
/reputationpage with the audit helper script and searching for
(-1). There's currently no work around for upvotes that I know of...
/reputationpage - stackoverflow.com/reputation. And finally, remember they won't show up if the post is deleted.