Three things can definitely help:
On the Extract Data screen:
1. If not all the data will be used, then apply a filter. There's no need to pull records from 2011 if you are only reporting from 2012 on.
2. Select the "Hide Unused Fields" option. This will hide any fields that are not used in any view in the workbook. Any unused field will not be included in the extract.
3. Check Aggregate Data for Visible dimensions. This will cause the extract to aggregate the raw records into summary data for the extract (at the highest level of aggregation possible given what is currently visible in each view).
Any one of these or some combination can dramatically reduce extract size. Be aware that #1 and #3 have the potential for impacting the functionality of your views (if you want to be able to drill into lower levels of detail or see data that was excluded in the filter). #2 is relatively safe to always apply.
(4. Upgrade to Tableau 8 when it is available [slated for release at the end of this month] as it has far better compression for text fields in extracts.)