More info on the topology would help us provide you the optimal solution.
You can configure two HSRP groups on the 3825s and add two default routes on the layer 3 device connected to the 3825s to load balance outbound traffic.
3825_1:
int f0/0
172.16.1.1 255.255.255.0
standby 1 ip 172.16.1.3
standby 1 priority 150
standby 2 ip 172.16.1.254
3825_2
ip add 172.16.1.2 255.255.255.0
standby 1 ip 172.16.1.3
standby 2 ip 172.16.1.254
standby 2 priority 150
On the router/layer 3 device connecting to the two 3825s, add two static routes as follows.
ip route 0.0.0.0 0.0.0.0 172.16.1.3
ip route 0.0.0.0 0.0.0.0 172.16.1.254
This would make the traffic leaving your network load balanced across both 3825s. To load balance inbound traffic from the Internet provide more info on your topology like;
a. are you connected to one or two ISPs?
b. how many public IP blocks do you have? If you are using more than one ISP then which provider does the IP belong to?
c. Are you learning default route via BGP or partial/full routing from the ISP?
d. what's connected to the two 3825s on your end?
e. is running IGP an option on your inside router or firewall?
HTH
Sundar