No separate fund, but we have a budget line-item for travel, and it's rather large. Travel is a major priority for us, and is nearly the only "entertainment" money that we spend.
Early in our marriage we decided that when it came to budgeting for entertainment, travel was the priority. We made choices in our everyday spending in order to feed that priority over and above what we normally might have been able to put aside for it. Among other things, we drive plain vehicles and keep them for a long time, we never buy alcohol in restaurants, we don't do recreational activities like golf that have a regular fee involved, and we didn't buy subscription TV until about 6 years ago (we've been married for 23 years.). We also use pre-paid wireless phones and we don't eat out very often when not traveling. All that helps add up to several thousand dollars a year that is always there for travel whenever we want to go somewhere.