I've been doing exactly that for a while now, and I felt like sharing about 2 tools I find very useful to do that (Feedity, to create free RSS feed from a website, and Update Scanner, a firefox add-on) through some examples (GoKunming's classified, GoKunming's calendar).
It's been a while since I have been using this service and it proved itself to be quite valuable. It's not that easy to set-up but when it finally works the way you want to (if it ever does), it's great.
For example, GoKunming has a feed for its article section but not for its classified section. And if you live in Kunming, you might wanna keep a look on that without having to visit the site everyday. Well, that's what RSS feeds are for, right?
Feedity let me create this feed which is working well for now. Might not work forever as it depends on how the website is built. if the said website change something, it might not work anymore. You then have to create it again if it's still possible.
This tool proved to be useful when feedity was no help. Because it's not always possible to create the feed you want.
Then, this Firefox Add-on will help you to scan regularly the webpage you want to find if anything changed. It will even tell you what changed!
For example, look at that calendar page on GoKunming... I've tried to create a feedity feed for it, but it didn't work. So I've just added the page to the Update Scanner list : Whenever they add events there, I know it quickly (you can set up how often it should scan the page):
Well, if a website doesn't give you what you want, you might be able to get it anyway. It's not perfect, I wish all webmasters would use modern tools... (and opening up their site). Sometimes, you can also ask for it, like I asked GoKunming to have a RSS feed and got it. I've been wanting to do another wishlist for them but it's just too damned long...
But I'm ranting... This post is about how to keep an eye on website you love but don't have RSS feeds :-)
[update] sorry, comment section is missing because of a blogger-Disqus issue I'm trying to fix. please email/twitter me. or comment on friendfeed.
[update2] Funny how GoKunming just changed its calendar page - to something worst - the same day I published this. When I say worst... just check it out.
[update3] March 12, 2009. Calendar has been improved from last time. Now you get all the month events on the page again. so it means you can use "Update scanner" again! Let me see if I can make Feedity feed...
[update4] not so good but here it is: