Paul
A great type of variable star to practice on are SXPHE type stars. They have very short cycles of up to 0.5 mag.
An easy example is BQ Ind
Go to here
http://www.aavso.org/vsx/index.php?view=search.top
Push the "more " button until you have the "var type" button visible and enter SXPHE
Select "order by" to RA and search. This will give you a reasonable selection. Most have periods of 50 mins to a few hours.
BX Scl has a period of ~50 mins and varies by 0.2 mag.
good luck.