Like a lot of people, I've become fairly frustrated with the lack of internal memory on my Wildfire S.
Googling reveals some obvious solutions, eg. move apps to the SD card, clear caches, etc.
There is one other thing you can do - if you don't use some of the pre installed apps. For example, I never use the YouTube app or the GMail app. If you go to these apps in the manage applications menu, you will probably find that they have been updated to newer versions. If so there will be a button marked Uninstall updates. Press this to revert the application to the default version that came with the phone. This should save you a fair bit of memory as it seems that the newer versions are stored alongside the original.
You may also need to turn off automatic updates for the original versions and you'll have to ignore any nag screens telling you that there are new versions available.
If you ever need to use the apps in the future, you can just update the to latest version in the normal way.
Removing updates for three or four apps saved me nearly 20Mb.
UPDATE: OK, so it doesn't work for all of them. Some apps, eg. GMail seem to just update themselves again, but not all of them.