C:\Windows\Temp usually gets a lot.
Also the ldscan folder (in \\server\ldmain) has an errorscan folder, and possibly a storage folder that can both be removed.
Other than that you'd probably want to find out where your space is being used.
One thing to watch for is what patches are you having downloaded.
Go into "Download Updates" and make sure you only have "For detected definitions only" selected.
You can delete items in the patch folder and then run a download, those patches that are still needed will re-download, though any patch jobs you have running could fail until the downloading completes.
Another location to consider nuking files from are is the IIS Logs, they are located in C:\WINDOWS\system32\LogFiles\W3SVC1
I find these get pretty big.
check in LDMAIN and LDLOGON directories for old log files.
Sometimes (depends on inventory scanner settings, I forgot...) you'll find tons of old huge inventory scanner logfiles.
Another "nice" place for old logs is the below ldmain\ldscan\ErrorScan or ldmain\ldscan\ErrorBigScan...
In ldmain\landesk\files you can find a lot of *.pmf files from the started console too.