A lot of the functionality I aimed to provide has been included in SE proper since then, so most of it I've just let it sit and decay (global search and moderator analytics are the two big ones).
That said, the one app that I've not actively developed (Column 80), because of its incredible simplicity) but still check every now and again is still getting traffic. Traffic heavilly spiked in June 2010 (due to the contest, fresh entry, etc) but still gets regular monthly traffic of around 100-150 users a month which is about what I would expect for such a niche app.
Yes, I'm still keeping my applications as up to date as I can with the time I have. Obviously this is not as often as I'd like, but I do the best I can. Even after the contest, I still added 2 or 3 new apps to StackApps.
Are you getting traffic/popularity?
The ones that were doing well before are still doing fairly well. Of particular interest is Stack2RSS, which has been swamped with traffic from feed aggregators and browsers.
I'm promoting my app on Meta when it solves some printer-friendly issues.
I don't think my apps properly fit in opensource advertising.
Are you going to monetize it in some way?
I've tried to add a couple of experimental inobstrusive ads links to pay the Google App Engine overquota's bill but never got a click in months, it's not a problem though since GAE quotas are fairly generous.