If you're looking for a meeting place or a good stop around ½ or halfway between Ashburn and California, MD, you can try Clinton, MD, which is almost an hour southeast of Ashburn, or almost an hour northwest of California, MD.
Other possible places to stop near the midpoint include Oxon Hill, and Camp Springs.
About ¼ or a fourth of the way, you can stop at Annandale, VA. This is about half an hour southeast of Ashburn.
About ⅓ or a third of the way, you can stop at Franconia, VA. This is about half an hour southeast of Ashburn.
About ⅔ or two thirds of the way, you can stop at Marbella, MD. This is a little over 1 hour southeast of Ashburn, or almost an hour northwest of California, MD.
About ¾ or three fourths of the way, you can stop at Hidden Valley, MD. This is about 1½ hours southeast of Ashburn, or about half an hour northwest of California, MD.
If you drive straight through without stopping at all, the total distance is 95 miles. The distances shown above don't include local roads to get into each town, so if you're planning a long road trip, make sure you factor in traffic and road conditions, rest stop breaks, and interesting detours along the way. If you're in a rush, you can do the trip with zero stops, and your total travel time would be around 1 hour, 50 minutes.